Secondary cell charger and charging method

ABSTRACT

An equipment and method for charging a secondary battery are provided to quickly and surely charge a secondary battery (secondary batteries) while preventing the secondary battery (batteries) from overcharging or insufficient charging. Special charging voltage E s  is applied to a secondary battery for a predetermined time, and then the applied voltage is switched to equilibrium voltage E eq  for establishing equilibrium cell potential of the secondary battery in its fully charged condition, wherein the special charging value E s  is larger than the equilibrium value E eq . Electric current i is detected while application of the equilibrium voltage E eq . If the detected electric current i is larger than standard electric current J for finishing charging, the above detection and charging are repeated; otherwise, charge of the secondary battery  1  is halted.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP03/06168, filed on May 16, 2003, whichclaims priority of Japanese Patent Application Nos. 2002-142598,2002-142599, 2002-142605, 2002-142606, which were filed on May 17, 2002and 2002-213625, filed on July 23, 2002. The International Applicationwas published under PCT Article 21(2) in a language other than English.

FIELD OF THE ART

The present invention relates to a charging equipment and chargingmethod for a secondary battery, such as a storage battery, anickel-cadmium battery, a nickel metal hydride battery, a lithium-ionbattery, and the like.

BACKGROUND ART

Recently, the range of use of a secondary battery is remarkablyincreasing. For example, the secondary battery is used as power sourceof an electrical appliance, e.g., a digital camera, a digital videocamera, and a notebook computer; a communication device, e.g., acellular phone; a power apparatus, e.g., an electric power tool and avacuum cleaner; or the like. The term “the secondary battery” means arechargeable battery that can repeat charge and discharge cycles, andduring charge, electrical energy is transformed into chemical energystored in the secondary battery. The stored chemical energy is convertedback into electrical energy so as to be used. A nickel-cadmium battery,a nickel metal hydride battery, a lithium ion battery, a NAS battery,etc. are listed as practically used secondary batteries.

Incidentally, the electromotive reaction and the discharge reactioninside the secondary battery include chemical reaction, electricreaction, and complicated energy conversion and energy transfer wherethe chemical reaction and the electric reaction are mutually concerned.There lies time element among these various reactions. Accordingly, thesecondary battery must be charged in consideration of the reactions, andwhen excessive current flows through the secondary battery in theprocess of charge, the internal structure of the secondary battery issometimes damaged by irreversible chemical reactions, includingunexpected exothermic reaction, swelling reaction, or the like. Even ifthe internal structure of the secondary battery is not damaged, it isdegraded so that the battery life becomes shorter, and effective cycleof the battery is decreased.

Conventionally, as disclosed in many patent applications, to charge thesecondary battery appropriately, a program for changing voltage to thesecondary battery with the passage of charging time is programmed into acharge control device of a charging equipment for the secondary battery,so that the voltage controlled according to the program is applied tothe secondary battery. The end of charge of a battery is judged andcontrolled on the basis of detection of the battery voltage as avariable controlled by a charging equipment, where a voltage detectiondevice for detecting voltage of the secondary battery is provided.

For example, the charging equipment for a secondary battery disclosed inthe Japanese Patent Laid Open Gazette Hei. 8-9563 comprises a voltagedetection circuit for detecting the minus potential difference ofcharging voltage applied to a battery with constant current, atemperature detection circuit for detecting change of the batterytemperature per unit time (temperature differential value) generated inthe charged battery with constant current, and a charge control circuitfor controlling an on-off switching for charging basing on comparing theminus potential difference detected by the voltage detection circuit andthe temperature differential value detected by the temperature detectioncircuit with their respective preset standard values. If the minuspotential difference and the temperature differential value reach theirpreset standard values thereof respectively, charging of the battery ishalted. In this way, there is such well-known conventional chargingcontrol device which observes the charged condition of a battery on thebasis of detection the battery voltage or the temperature serving as acontrolled variable and judges whether charge of the charging batteryshould be finished or not.

However, when the method for deciding end of charging basing theabove-mentioned variable is simply applied in disregard of the chargedcondition of the secondary battery, various problems arise as follows:The characteristic property of the secondary battery during its chargingvaries according to variation of an electrode, an electrolyte, astructure, or another element of the charged secondary battery. Even ifthe secondary batteries are of the same kind or marked with the sametype code, the characteristic property thereof varies with thedifference of an environmental condition during charge, a use history,an electrochemical itinerancy in the secondary battery, and the like.Therefore, a battery charged according to the conventional controlmethod may be overcharged, where the problem arises that abnormalchemical reactions (irreversible chemical reactions) occurs inside thesecondary battery so as to generate heat, that is, electrical energy istransformed into heat energy, whereby the charging efficiency may bedecreased, and gas may be generated in the secondary battery so as toincrease the internal pressure thereof and cause the leak of liquid fromthe secondary battery. Therefore, the solid internal structure of thesecondary battery required for repeating charge and discharge cycles isso damaged as to decrease effective battery cycles of the secondarybattery.

Moreover, it is desirable that the charging time of the secondarybattery is as short as possible. However, as mentioned above, theconventional charging control device using the fixed charge controlpattern applies the same voltage to any type of secondary. Therefore, ifa secondary battery is charged by voltage lower than its rated voltage,it takes quite a long time to fully charge the secondary battery. Inaddition, the conventional device inconveniently has no means forinforming a user how much electricity the secondary battery to becharged stores, and how long it takes to charge the secondary battery.

SUMMARY OF THE INVENTION

It is a general object of the invention to provide a charging equipmentfor a secondary battery, which can charge a secondary battery or variouskinds of secondary batteries rapidly and certainly preventing thesecondary battery or batteries from overcharging or insufficientcharging, or which is easy to use.

A first aspect of a charging equipment for a secondary battery accordingto the present invention comprises: a voltage supply means for applyingvoltage to the secondary battery; a current detection means fordetecting electric current flowing through the secondary battery; and acharge control device for controlling charge of the secondary battery.The charge control device includes: a storage means storing equilibriumvoltage and special charging voltage corresponding to the secondarybattery to be charged; a switching means; and a judging means. Theequilibrium voltage is provided for establishing equilibrium cellpotential of the secondary battery in a fully charged condition, and thespecial charging voltage is provided for supplying the secondary batterywith charging electric current of peak or almost peak value. The specialcharging voltage is larger than the equilibrium voltage and does notreach a region of voltage causing irreversible chemical reaction in thesecondary battery. The switching means is provided for switching voltagesupplied by the voltage supply means between the equilibrium voltage andthe special charging voltage. The judging means is provided for judgingwhether electric current detected by the current detection means duringapplication of the equilibrium voltage is larger than a preset standardelectric current for finishing charging or not.

The charge control device controls charge of a secondary battery byfirst to fourth steps:

-   -   the first step of applying the special charging voltage to the        secondary battery set in the charging equipment for a        predetermined time;    -   the second step of switching voltage applied to the secondary        battery from the special charging voltage to the equilibrium        voltage;    -   the third step of detecting electric current flowing through the        secondary battery by the current detection means while applying        the equilibrium voltage to the secondary battery for a short        time; and    -   the fourth step of returning to the first step and repeating the        above steps if the judging means judges that the detected        electric current is larger than the standard electric current        for finishing charging; otherwise, halting the secondary        battery.

The charging equipment of the first aspect can remarkably increaseeffective battery cycles of a secondary battery because it can chargethe secondary battery appropriately without causing excessive damagingchemical reaction (oxidation-reduction reaction) in the secondarybattery until the secondary battery is fully charged. Particularly, thecharging equipment can reduce charge time because it mainly applies thepredetermined charging voltage, which is larger than the equilibriumvoltage, so as to supply a secondary battery with pretty large chargingcurrent. Furthermore, the charging equipment can accurately bring thesecondary battery into the fully charged condition because itperiodically applies the equilibrium voltage to the secondary battery tocheck the charged condition of the secondary battery.

A second aspect of a charging equipment for a secondary batteryaccording to the present invention is similar with that of the firstaspect except that the storage means of the charge control devicepreviously stores the equilibrium voltages and the special chargingvoltages corresponding to various kinds of secondary batteries. Whendata of a kind of secondary battery to be charged is inputted to thecharge control device, the equilibrium voltage and special chargingvoltage in correspondence to the kind of secondary battery to be chargedare selected from a table of the storage means so as to charge the kindof secondary battery basing on the selected equilibrium voltage andspecial charging voltage.

By the charging equipment of the second aspect, a user can manuallyselect the suitable equilibrium voltage and special charging voltage incorrespondence to the kind of secondary battery to be charged from atable of the storage means, thereby ensuring appropriate charge ofelectricity to the kind of secondary battery without causing excessivechemical reaction (oxidation-reduction reaction) in the secondarybattery until the secondary battery is fully charged. As a result, thecharging equipment does not give any damage to the internal structure ofthe secondary battery, so that it can further increase effective batterycycles of the secondary battery. Particularly, the charging equipmentcan reduce charge time because it supplies the secondary battery withpretty large charging current by mainly applying the special chargingvoltage larger than the equilibrium voltage. Furthermore, the chargingequipment can accurately bring the secondary battery into the fullycharged condition because it periodically applies the equilibriumvoltage to the secondary battery to check the charging state of thesecondary battery.

A third aspect of a charging equipment for a secondary battery accordingto the present invention is almost the same apparatus as that of thefirst aspect, but the storage means of the charge control device of thethird aspect previously stores the n (n is a natural number largerthan 1) equilibrium voltages and the n special charging voltagescorresponding to n kinds of secondary batteries. The charge controldevice controls charge of a secondary battery by first to eighth steps:

the first step of initializing a counter variable k (k=1,2, . . . ,n) to1;

the second step of applying the kth smallest voltage of the n specialcharging voltages to the secondary battery set in the charging equipmentfor a predetermined time;

the third step to jumping to the sixth step if k is equal to n;

the fourth step of detecting voltage applied to the secondary battery bythe voltage detection means while applying the kth smallest specialcharging voltage to the secondary battery for the predetermined time;

the fifth step of incrementing k by 1 and returning to the second stepif the voltage judging means judges that the detected voltage is largerthan the kth smallest special charging voltage; otherwise, passing tothe sixth step;

the sixth step of switching voltage applied to the secondary battery tothe kth smallest voltage of the n equilibrium voltages;

the seventh step of detecting electric current flowing through thesecondary battery by the current detection means while applying the kthsmallest equilibrium voltage to the secondary battery for a short time;and

the eighth step of returning to the second step and repeating the abovesteps if the current judging means judges that the detected electriccurrent is larger than the standard electric current for finishingcharging; otherwise, halting charge of the secondary battery Thecharging equipment of the third aspect gives the same effect as that ofthe first aspect to each kind of the secondary batteries to be charged.Additionally, the charging equipment of the third aspect automaticallyidentifies the kind of secondary battery in the process of charge and itgives appropriate charge of electricity to the kind of secondary batterybasing on the selected equilibrium voltage and special charging voltagewithout causing excessive damaging chemical reaction(oxidation-reduction reaction) in the secondary battery until the kindof secondary battery is fully charged.

A fourth aspect of a charging equipment for a secondary batteryaccording to the present invention is almost the same apparatus as thatof the third aspect, but the charge control device of the chargingequipment of the fourth aspect further includes a voltage differencejudging means for judging whether a difference of voltage detected bythe voltage detection means during application of the special chargingvoltage between a present value and a past value is within a presetrange or not, and it controls charge of a secondary battery by first toeighth steps:

the first step of initializing a counter variable k (k=1,2, . . . ,n) to1;

the second step of applying the kth smallest voltage of the n specialcharging voltages to the secondary battery set in the charging equipmentfor a predetermined time;

the third step of jumping to the sixth step if k is equal to n; thefourth step of detecting voltage applied to the secondary battery by thevoltage detection means while applying the kth smallest special chargingvoltage to the secondary battery for the predetermined time;

the fifth step of passing to the sixth step if the voltage detection isthe first time or the voltage difference judging means judges that thedetected voltage difference is within the range; otherwise, incrementingk by 1 and returning to the second step;

the sixth step of switching voltage applied to the secondary batteryfrom the kth smallest special charging voltage to the kth smallestvoltage of the n equilibrium voltages;

the seventh step of detecting electric current flowing through thesecondary battery by the current detection means while applying the kthequilibrium voltage to the secondary battery for a short time; and

the eighth step of returning to the second step and repeating the abovesteps if the current judging means judges that the detected electriccurrent is larger than the standard value of electric current forfinishing charging; otherwise, halting charge of the secondary battery.

The charging equipment of the fourth aspect has the same effect as thatof the first aspect. Additionally, the charging equipment of the fourthaspect automatically identifies the kind of secondary battery in theprocess of charge and it gives appropriate charge of electricity to thekind of secondary battery basing on the selected equilibrium voltage andspecial charging voltage without causing excessive damaging chemicalreaction (oxidation-reduction reaction) in the secondary battery untilthe kind of secondary battery is fully charged.

A fifth aspect of a charging equipment for a secondary battery accordingto the present invention comprises: a voltage supply means for applyingvoltage to the secondary battery; a voltage detection means fordetecting open-circuit voltage of the secondary battery; and a chargecontrol device for controlling charge of the secondary battery. Thecharge control device includes: a storage means storing special chargingvoltage for supplying the secondary battery with charging electriccurrent of peak or almost peak value, wherein the special chargingvoltage is larger than equilibrium voltage for establishing equilibriumcell potential of the secondary battery in a fully charged condition anddoes not reach a region of voltage causing irreversible chemicalreaction in the secondary battery; and a voltage difference judgingmeans for judging whether a voltage difference between the chargingvoltage and the open-circuit voltage of the secondary battery is largerthan a preset standard value or not. The charge control device controlscharge of a secondary battery by first to third steps:

the first step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time, and thenshutting off the charging voltage from the secondary battery;

the second step of detecting the open-circuit voltage of the secondarybattery by the voltage detection means, and computing the voltagedifference between the special charging voltage and the open-circuitvoltage of the secondary battery; and

the third step of returning to the first step and repeating the abovesteps if the voltage difference judging means judges that the computedvoltage difference is larger than the standard value; otherwise, haltingcharge of the secondary battery.

The charging equipment of the fifth aspect remarkably increaseseffective battery cycles of the secondary battery because it can chargethe secondary battery appropriately without causing excessive damagingchemical reaction (oxidation-reduction reaction) in the secondarybattery until the secondary battery is fully charged. Additionally, bycomputing the voltage difference between the special charging voltage,which is larger than the equilibrium voltage, and the open-circuitvoltage of the secondary battery, the charging equipment can furtheraccurately judge whether the secondary battery reaches the fully chargedcondition or not. Furthermore, the charging equipment can reduce chargetime because it mainly applies the special charging voltage, which islarger than the equilibrium voltage, so as to supply the secondarybattery with pretty large charging current.

A sixth aspect of a charging equipment for a secondary battery accordingto the present invention is almost the same apparatus as that of thefifth aspect, but the charge control device of the charging equipment ofthe sixth aspect has a judging means for judging whether theopen-circuit voltage of the secondary battery detected by the voltagedetection means is larger than the equilibrium voltage as a standardvalue or not, instead of the above-mentioned voltage difference judgingmeans. The charge control device of the sixth aspect controls charge ofa secondary battery by first to third steps:

the first step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time, and thenshutting off the charging voltage from the secondary battery;

the second step of detecting the open-circuit voltage of the secondarybattery by the voltage detection means, and computing the voltagedifference between the special charging voltage and the open-circuitvoltage of the secondary battery; and

the third step of returning to the first step and repeating the abovesteps if the judging means judges that the detected open-circuit voltageis smaller than the equilibrium voltage as the standard voltage;otherwise, halting charge of the secondary battery.

The charging equipment of the sixth aspect can remarkably increaseeffective battery cycles of the secondary battery because it can chargethe secondary battery appropriately without causing excessive damagingchemical reaction (oxidation-reduction reaction) in the secondarybattery until the secondary battery is fully charged. Additionally, thecharging equipment can reduce charge time because it mainly applies thespecial charging voltage larger than the equilibrium voltage so as tosupply the secondary battery with pretty large charging current.

A seventh aspect of a charging equipment for a secondary batteryaccording to the present invention comprises: a voltage supply means forapplying predetermined voltage to the secondary battery; a currentdetection means for detecting electric current flowing through thesecondary battery while applying the predetermined voltage to thesecondary battery; and a charge time predicting means for estimating atime required for fully charging the secondary battery basing on thedetected electric current.

By the easy method of detecting electric current, the charging equipmentof the seventh aspect can decide the time required for fully chargingthe secondary battery, thereby being useful.

The time required for fully charging the secondary battery may bedefined as a time for the electric current detected by the currentdetection means to reach standard electric current for finishingcharging. The charging equipment of this type may stop charging thesecondary battery when the detected electric current is not larger thanthe standard electric current for finishing charging.

The charging equipment can remarkably increase effective battery cyclesof the secondary battery because it periodically checks the chargingstate of the secondary battery so as to charge the secondary batteryappropriately without causing excessive damaging chemical reaction(oxidation-reduction reaction) in the secondary battery until thesecondary battery is fully charged.

Alternatively, the charging equipment may stop charging the secondarybattery simply after the passage of the time required to fully chargethe secondary.

An eighth aspect of a charging equipment for a secondary batteryaccording to the present invention comprises: a voltage supply means forapplying predetermined voltage to the secondary battery; a currentdetection means for detecting electric current flowing through thesecondary battery when applying the predetermined voltage to thesecondary battery; and a charging rate computing means for computing thecharging rate of the secondary battery at the moment when the currentdetection means detects the electric current.

The charging equipment of the eighth aspect is useful because it decideshow much the secondary battery is charged at present by the easy methodof detecting a value of electric current.

In each of the charging equipments of the seventh and eighth aspects,the voltage supply means applies charging voltage, which is larger thanthe above-mentioned predetermined voltage, to the secondary battery fora determined time, and then the switching means switches applied voltagefrom the charging voltage to the predetermined voltage, and the currentdetection means detects electric current flowing through the secondarybattery for the moment during application of the predetermined voltageto the secondary battery.

Consequently, each of the charging equipments can reduce charge timebecause it mainly applies the charging voltage which is larger than thepredetermined voltage so as to supply the secondary battery with prettylarge charging current.

A ninth aspect of a charging equipment for a secondary battery accordingto the present invention comprises: a voltage supply means for applyingvoltage to the secondary battery; a current detection means fordetecting electric current flowing through the secondary battery; and acharge control device for controlling charge of the secondary battery.The charge control device includes: a storage means storing equilibriumvoltage and special charging voltage corresponding to the secondarybattery to be charged; a switching means; and a charge time predictingmeans. The equilibrium voltage is provided for establishing equilibriumcell potential of the secondary battery in a fully charged condition.The special charging voltage is provided for supplying the secondarybattery with charging electric current of peak or almost peak value. Thespecial charging voltage is larger than the equilibrium voltage and doesnot reach a region of voltage causing irreversible chemical reaction inthe secondary battery. The switching means is provided for switchingvoltage supplied by the voltage supply means between the equilibriumvoltage and the special charging voltage. The charge time predictingmeans is provided for estimating a time required for fully charging thesecondary battery basing on the detected electric current. The chargecontrol device controls charge of a secondary battery by first to sixthsteps:

the first step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time;

the second step of switching voltage applied to the secondary batteryfrom the special charging voltage to the equilibrium voltage;

the third step of detecting electric current flowing through thesecondary battery by the current detection means while applying theequilibrium voltage to the secondary battery for a short time;

the fourth step of predicting a time required for fully charging thesecondary battery by the charge time predicting means basing on thedetected electric current;

the fifth step of switching voltage applied to the secondary batteryfrom the equilibrium voltage to the special charging voltage; and

the sixth step of halting charge of the secondary battery after thelapse of the time required to fully charge the secondary.

The charging equipment of the ninth aspect can reduce charge timebecause it mainly applies the special charging voltage, which is largerthan the equilibrium voltage, so as to supply the secondary battery withpretty large charging current. The charging equipment is availablebecause it facilitates easy check of the fully charged condition of anykind of secondary battery because electric current detected by thecurrent detection means is substantially zero if a secondary batterydetected by the current detection means while being supplied with theequilibrium voltage reaches its fully charged condition, and because itcan precisely predict the time required for fully charging the secondarybattery. Since the charging equipment stops changing the secondarybattery just after the passage of the predicted time so as to helpscycle life of the secondary battery become far and away longer, thesecondary battery is appropriately charged without excessive damagingchemical reaction (oxidation-reduction reaction) therein until its fullycharged condition, thereby increasing its effective battery cycles.

A tenth aspect of a charging equipment for a secondary battery accordingto the present invention comprises: a voltage supply means for applyingvoltage to the secondary battery; a current detection means fordetecting electric current flowing through the secondary battery; and acharge control device for controlling charge of the secondary battery.The charge control device includes: a storage means storing equilibriumvoltage and special charging voltage; a switching means; a charging ratecomputing means; and a judging means. The equilibrium voltage isprovided for establishing equilibrium cell potential of the secondarybattery balanced in a fully charged condition. The special chargingvoltage is provided for supplying the secondary battery with chargingelectric current of peak or almost peak value. The special chargingvoltage is larger than the equilibrium voltage and does not reach aregion of voltage causing irreversible chemical reaction in thesecondary battery. The switching means is provided for switching voltagesupplied by the voltage supply means between the equilibrium voltage andthe special charging voltage. The charging rate computing means isprovided for computing a charging rate of the secondary battery at themoment when the current detection means detects electric current. Thejudging means is provided for judging whether the charging rate computedby the charging rate computing means is larger than a preset standardvalue or not. The charge control device controls charge of a secondarybattery by first to fifth steps:

the first step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time;

the second step of switching voltage applied to the secondary batteryfrom the special charging voltage to the equilibrium voltage;

the third step of detecting electric current flowing through thesecondary battery by the current detection means while applying theequilibrium voltage to the secondary battery for a short time;

the fourth step of computing the charging rate of the secondary batteryby the charging rate computing means at the moment when the electriccurrent is detected; and the fifth step of returning to the first stepand repeating the above steps if the judging means judges that thecomputed charging rate is not larger than the standard value; otherwise,halting charge of the secondary battery.

The charging equipment of the tenth aspect can reduce charge timebecause it mainly applies the special charging voltage, which is largerthan the equilibrium voltage, so as to supply the secondary battery withpretty large charging current. The charging equipment is availablebecause it facilitates easy check of the fully charged condition of anykind of secondary battery because electric current detected by thecurrent detection means is substantially zero if a secondary batterydetected by the current detection means while being supplied with theequilibrium voltage reaches its fully charged condition, and because itcan precisely predict the present charging rate of the secondarybattery. Since the charging equipment stops changing the secondarybattery just after the passage of the predicted time so as to helpscycle life of the secondary battery become far and away longer, thesecondary battery is appropriately charged without excessive damagingchemical reaction (oxidation-reduction reaction) therein until its fullycharged condition, thereby increasing its effective battery cycles.

An eleventh aspect of a charging equipment for a secondary batteryaccording to the present invention comprises: a circuit for connecting asecondary battery and a capacitor to a power supply in parallel; and aswitching means for making/breaking a closed loop circuit for connectingthe secondary battery to the capacitor. The charging equipment brakesthe closed loop circuit for a predetermined time and applies voltage tothe capacitor from a power source so as to store up electricity in thecapacitor, and then, the charging equipment makes the closed loopcircuit so as to transmit the electricity stored in the capacitor to thesecondary battery.

The charging equipment of the eleventh aspect facilitates for easilymeasuring how much electricity is charged into the secondary battery.Additionally, by using the capacitor as a charging medium, the chargingequipment can charge much electricity, i.e., large electric current tothe secondary battery for a short time, thereby reducing charge time.Moreover the charging equipment can economically charge without anexpensive high-current circuit, and control its charging very easily,thereby improving its reliability.

A twelfth aspect of a charging equipment for a secondary batteryaccording to the present invention comprises: a checking power supplyfor applying special charging voltage to the secondary battery; acurrent detection means for detecting electric current flowing to thesecondary battery; and a current judging means for judging whetherelectric current detected by the current detection means duringapplication of the special charging voltage is larger than a presetstandard electric current for finishing charging. While the closed loopcircuit is broken, the check power source applies the secondary batterywith the special charging voltage, and electric current flowing to thesecondary battery from the check power source is detected and comparedwith the standard electric current for finishing charging. If thedetected electric current is larger than the standard electric currentfor finishing charging, said storage of electricity in the capacitor andtransmission of electricity to the secondary battery are repeated;otherwise, charge of the secondary battery is halted.

The charging equipment of the twelfth aspect can increase effectivebattery cycles of the secondary battery because it charges the secondarybattery appropriately without causing excessive damaging chemicalreaction (oxidation-reduction reaction) in the secondary battery untilthe secondary battery is fully charged. The charging equipment canfurther reduce charge time because it makes the charged condition of thesecondary battery observable while the capacitor stores electric charge.

Preferably, equilibrium voltage for equilibrium cell potential of thesecondary battery in a fully charged condition serves as the specialcharging voltage. Accordingly, the charging equipment can easily andaccurately decide whether a secondary battery is fully charged or notbecause any secondary battery can be decided to be fully charged whenthe detected electric current is not larger than zero.

A thirteenth aspect of a charging equipment for a secondary batteryaccording to the present invention further comprises: a voltagedetection means for detecting open-circuit voltage of the secondarybattery; and a voltage judging means for judging whether theopen-circuit voltage of the secondary battery detected by the voltagedetection means is larger than equilibrium voltage for equilibrium cellpotential of the secondary battery in a fully charged condition. Whilethe closed loop circuit is broken, the open-circuit voltage of thesecondary battery is detected and compared with the equilibrium voltage.If the open-circuit voltage is smaller than the equilibrium voltage,said storage and transmission are repeated; otherwise, charge of thesecondary battery is halted.

The charging equipment of the thirteenth aspect can increase effectivebattery cycles of the secondary battery because it charges the secondarybattery appropriately without causing excessive damaging chemicalreaction (oxidation-reduction reaction) in the secondary battery untilthe secondary battery is fully charged. The charging equipment canfurther reduce charge time because it makes the charged condition of thesecondary battery observable while the capacitor stores electric charge.

A fourteenth aspect of a charging equipment for a plurality of secondarybatteries according to the present invention comprises: a chargingvoltage control means for applying charging voltage to a secondarybattery; a control means for monitoring a charged condition of thesecondary battery; and a battery switching means for switching asecondary battery selected among the plurality of secondary batteries tobe charged basing on a signal for finishing charging issued from thecontrol means.

The charging equipment of the fourteenth aspect can surely charge eachsecondary battery by monitoring the charged condition of the secondarybattery, thereby causing neither insufficiently charged secondarybattery nor over-charged secondary battery, which may be damaged by itsinner excessive chemical reaction (oxidation-reduction reaction).Consequently, effective battery cycles of each secondary battery can beremarkably increased.

The charging equipment of the fourteenth aspect may further comprise: achecking voltage control means for applying equilibrium voltage to asecondary battery while monitoring a charged condition of the secondarybattery, the equilibrium voltage for equilibrium cell potential of thesecondary battery in a fully charged condition; a voltage switchingmeans for switching voltage between the charging voltage and theequilibrium voltage, that is, checking voltage; and a current detectionmeans for detecting electric current flowing through the secondarybattery to which the check voltage is applied. The control meansmonitors a charged condition of the secondary battery basing on thesignal from the current detection means.

When charging each secondary battery, this charging equipment can graspthe charged condition of the secondary battery by the easy method ofdetecting electric current while periodically applying the checkingvoltage thereto. Therefore, the charging equipment can charge eachsecondary battery appropriately without causing excessive chemicalreaction (oxidation-reduction reaction) therein until the secondarybattery is fully charged, whereby no insufficiently charged secondarybattery occurs.

Alternatively, the charging equipment of the fourteenth aspect mayfurther comprise: a voltage switching means for switching on/offapplication of charging voltage to the secondary battery; and a voltagedetection means for detecting open-circuit voltage of a secondarybattery while switching off application of charging voltage thereto. Theabove-mentioned control means monitors how much the secondary battery ischarged basing on the signal from the voltage detection means.

When charging each secondary battery, the charging equipment can graspthe state of charge of each of the secondary batteries by the easymethod of detecting open-circuit voltage while periodically stoppingapplying charging voltage. Therefore, the charging equipment can chargeeach secondary battery appropriately without causing excessive chemicalreaction (oxidation-reduction reaction) therein until the secondarybattery is fully charged, whereby no insufficiently charged secondarybattery remains.

Further alternatively, in the charging equipment of the fourteenthaspect, the charging voltage may be set to a special charging voltagefor supplying the secondary battery with charging electric current ofpeak or almost peak value, wherein the special charging voltage islarger than equilibrium voltage for equilibrium cell potential of thesecondary battery in a fully charged condition and does not reach aregion of voltage causing irreversible chemical reaction in thesecondary battery.

Consequently, the charging equipment mainly applies the special chargingvoltage, which is larger than the equilibrium voltage, to the secondarybattery so as to supply the secondary battery with pretty large chargingcurrent. Therefore, even by using the method for charging the pluralityof secondary batteries one by one, the time for charging each secondarybattery is reduced, thereby reducing the time for charging all of thesecondary batteries.

A fifteenth aspect of a charging equipment for a plurality of secondarybatteries according to the present invention comprises a batteryswitching means for switching a secondary battery to be charged from thelast charged secondary battery to an uncharged secondary battery, so asto charge the secondary batteries one by one.

The charging equipment of the fifteenth aspect can be easily controlledso as to surely charge all of the secondary batteries because it chargesthe secondary batteries one by one.

Preferably, the charging equipments of each of the foregoing aspects mayfurther comprise an informational means for giving information of a timerequired to fully charge the secondary battery, charging rate of thesecondary battery, or a charged condition of the secondary battery fordeciding whether charge of the secondary battery is finished or not,thereby being more available.

A sixteenth aspect of a charging equipment for a plurality of secondarybatteries according to the present invention comprises a voltage supplymeans for applying voltage to a secondary battery, wherein a group ofthe plurality of secondary batteries are connected to the voltage supplymeans in series. The charging equipment charges the secondary batteriesof the group one by one, switching from the last charged secondarybattery to the next uncharged secondary battery.

The charging equipment of the sixteenth aspect can surely charge each ofthe secondary batteries of the group so as to prevent them from beingovercharged or insufficiently charged even if the secondary batterieshave different characteristics. Therefore, each of the secondarybatteries charged by the charging equipment can provide its fullcapacity. Additionally, the charging equipment can increase effectivebattery cycles of the secondary batteries (or a packed power supplyconsisting of the plurality of the secondary batteries) and stably drivean apparatus to which the packed power supply gives electric power.

The concept of the sixteenth aspect is applicable for each of theforgoing charging equipments of the type which switches applied voltagebetween high voltage for high electric current and low voltage. Forexample, the charging equipment of the first aspect improved accordingto the sixteenth aspect can charge each of a plurality of secondarybatteries appropriately without overcharging and damaging its innerstructure, thereby contributing for increasing effective battery cyclesof each secondary battery and cost-saving. Moreover, the chargingequipment can reduce the time for charging each secondary battery bysupplying the secondary battery with pretty large charging current,thereby remarkably reduce total charge time for all of the secondarybatteries in the packed power supply. The packed power supply charged bythe charging equipment can reduce dead time when any apparatus to whichthe packed power supply applies electric power cannot work because ofshortage of battery, thereby enhancing availability of the apparatus.

Additionally, the charging equipment of the sixteenth aspect may have aplurality of the above-said groups connected to the voltage supply meansin parallel, wherein all secondary batteries of one group are completelycharged, and then each secondary battery of another next group ischarged.

This charging equipment can surely all the secondary batteries of theplurality of groups connected to the voltage supply means in parallel soas to provide a packed power supply capable of supplying large outputvoltage.

Preferably, the charging equipment of the sixteenth aspect cansimultaneously charge the plurality of groups of secondary batteries.

This charging equipment can simultaneously start charging the groups ofsecondary batteries and further reduce total charge time for chargingall the secondary batteries. Consequently, the packed power supplycharged by the charging equipment can reduce dead time when anyapparatus to which the packed power supply applies electric power cannotwork because of shortage of battery, thereby enhancing availability ofthe apparatus.

The charging equipment of the sixteenth aspect may be applied for usingthe plurality of groups of secondary batteries in either series orparallel.

Accordingly, the groups of secondary batteries may be selectively usedin either series or parallel corresponding to load. The chargingequipment prevents the secondary batteries in each of the groups frombeing overcharged and insufficiently charged, thereby ensuring that allthe secondary batteries provide their full capacities and prolong theirlives.

Of the above-mentioned charging equipments of various aspects, there aresome charging equipments of a type which stores equilibrium voltage andspecial charging voltage for charging a secondary battery and switchingvoltage between the equilibrium voltage and the special chargingvoltage, wherein the equilibrium voltage is provided for establishingequilibrium cell voltage of the secondary battery in a fully chargedcondition, wherein the special charging voltage is provided forsupplying the secondary battery with charging electric current of peakor almost peak value, and wherein the special charging voltage is largerthan the equilibrium voltage and does not reach a region causingirreversible chemical reaction in the secondary battery. This type ofcharging equipment may be provided with a short-circuit means forshort-circuiting the secondary battery between its terminals afterapplying the special charging voltage to a secondary battery and beforeswitching voltage to the equilibrium voltage.

The short-circuit means clears the electrode interface of a secondarybattery of electric charge, so that the charging equipment may switchcharging voltage to the equilibrium voltage smoothly and stably supplycharging electric current after the switching so as to accurately detecta value of electric current, thereby charging the secondary batteryappropriately.

A seventeenth aspect of a charging equipment for a secondary batteryaccording to the present invention comprises: a voltage supply means forapplying voltage to the secondary battery; a voltage detection means fordetecting voltage of the secondary battery; and a judging means forjudging whether voltage applied to the secondary battery detected by thevoltage detection means is larger than recharging voltage. Therecharging voltage is smaller than equilibrium voltage for equilibriumcell voltage of the secondary battery in a fully charged condition. Ifthe judging means judges that the detected voltage is not larger thanthe recharging voltage, the charging equipment recharges the secondarybattery by supplying the secondary battery with the charging voltagefrom the voltage supply means.

A secondary battery charged up by the charging equipment of theseventeenth aspect necessarily has effective voltage equal to or higherthan the recharging voltage just when it is picked out from the chargingequipment, thereby being available.

In the process of recharging, the charging equipment charges a secondarybattery appropriately without causing excessive damaging chemicalreaction (oxidation-reduction reaction) in the secondary battery untilthe secondary battery is fully charged, thereby remarkably increasingeffective battery cycles of the secondary battery and reducing the timefor the secondary battery to be fully charged.

An eighteenth aspect of a charging equipment for a secondary batteryaccording to the present invention repeats a charging operation cycleincluding check of a charged condition of a secondary battery andapplication of special charging voltage to the secondary battery for apredetermined time, wherein a relaxation time is established between thecharging operation cycles, and halts charge of the secondary batterywhen it is judged at the check that the secondary battery is fullycharged.

By establishing the relaxation time between the charging operationcycles, this charging equipment can accurately check the chargedcondition of the secondary battery in the next charging operation cycleso as to decide whether the secondary battery is fully charged or not,thereby being improved in reliability.

A nineteenth aspect of a charging equipment for charging a plurality ofsecondary batteries according to the present invention repeats acharging turn for charging the plurality of secondary batteries, andhalts charge of each secondary battery when it is judged at the checkthat the secondary battery is fully charged. The charging turn serves asa series of the charging operation cycles each of which is performed foreach uncharged secondary battery. The charging operation cycles areperformed one by one for the respective secondary batteries. Therelaxation time is established between the final charging operationcycle in one charging turn and the first charging operation cycle in thenext charging turn.

The charging equipment of the nineteenth aspect stops charging for therelaxation time between the charging operation cycle in one chargingturn and the first charging operation cycle in the next charging turn,so as to bring a surface of an electrode of the secondary battery into astable condition, thereby accurately checking the charged condition ofthe secondary battery in the nest charging turn so as to decide whetherthe secondary battery is fully charged or not.

Complementarily speaking, in the process of charging a secondarybattery, electrode reaction occurs on an electrode surface touchingelectrolyte. In this electrode reaction are simultaneously performedmovement of reactant to the electrode surface from the electrolyte,movement of electron between the reactant and the electrode, andmovement of product into the electrolyte from the electrode surface. Ittakes quite a long time for these movements so that the secondarybattery, if the charged state thereof is checked immediately afterpausing charge of the secondary battery, may be misread as if it reachedthe fully charged condition because of ion and the like beingelectrophoresed around the electrode surface. The relaxation time isadvantageous for preventing such misreading. The charging equipment ofthe nineteenth aspect rationally and effectively establishes therelaxation time as a partial process in a cycle of charging each ofsecondary batteries.

Each of the above-mentioned charging equipments of various aspects mayfurther comprise a cooling means for cooling an exothermic section init. This cooling means prevents the exothermic section such as anexothermic element from generating heat, which is unexpectedlytransmitted to the secondary battery so as to promote excessive chemicalreaction (oxidation-reduction reaction) in the secondary battery or tomislead the heat of the secondary battery to be regarded as heatgenerated by the secondary battery itself. Consequently, the secondarybattery is charged appropriately without damage of its inner structureuntil it is fully charged, thereby remarkably increasing its effectivebattery cycles.

A twentieth aspect of a charging equipment for a secondary batteryaccording to the present invention comprises a take-off means for takingoff the secondary battery from a seat of the charging equipment byone-touch operation, thereby being convenient for a user to take out thesecondary battery from the seat of the charging equipment easily.

In the charging equipment of the twentieth aspect, the take-off meansmay preferably comprise: an operation member to be pushed down by auser; a boost member for pushing up the secondary battery set on theseat; a pivot shaft for rotatably supporting the boost member; and anenergization means attached to the shaft, wherein the energization meansenergizes the boost member opposite to the direction of the boost memberbeing pushed up, and wherein, by operating the operation member, a partof the boost member arises or sinks above and below the seat.

Therefore, a user can easily pick up the charged secondary battery fromthe seat of the charging equipment by one-touchingly operating theoperation member for raising or sinking a part of the boost member.

Further, in the charging equipment for a secondary battery of thetwentieth aspect, the seat may be preferably recessed at one side in itslongitudinal direction so as to serve as the take-off means.

By using this convenient charging equipment, a user can easily take outthe secondary battery set on the seat of the charging equipment byone-touch operation. When a user pushes down one side part of thesecondary battery in its longitudinal direction, the other side part ofthe secondary battery arises so as to separate its both terminals fromthe seat.

It is another general object of the invention to provide a chargingmethod for charging a secondary battery or a plurality of secondarybatteries rapidly and certainly preventing the secondary battery orbatteries from overcharging or insufficient charging.

A first aspect of a charging method for a secondary battery according tothe present invention comprises the steps of:

(1) previously storing equilibrium voltage and special charging voltagefor charging the secondary battery, the equilibrium voltage equalingelectromotive force of the secondary battery in a fully chargedcondition, and the special charging voltage supplying the secondarybattery with charging electric current of peak or almost peak value,wherein the special charging voltage is larger than the equilibriumvoltage and does not reach a region of voltage causing irreversiblechemical reaction in the secondary battery;

(2) applying the special charging voltage to the secondary battery for adetermined time;

(3) switching voltage applied to the secondary battery from the specialcharging voltage to the equilibrium voltage;

(4) detecting electric current flowing through the secondary batterywhile applying the equilibrium voltage to the secondary battery for ashort time;

(5) comparing the detected value of electric current with a standardvalue of electric current for finishing charging; and

(6) returning to the step (2) and iterating the above steps when thedetected electric current is larger than standard electric current;otherwise halting charge of the secondary battery.

By the charging method of the first aspect, a secondary battery can becharged appropriately without excessive damaging chemical reaction(oxidation-reduction reaction) therein until it is fully charged,thereby remarkably increasing its effective battery cycles.Particularly, by the charging method, the special charging voltage,which is larger than the equilibrium voltage, is mainly applied to thesecondary battery so as to supply it with pretty large charging current,thereby reducing charging time.

A second aspect of a charging method for a secondary battery accordingto the present invention comprises:

previously storing n (n is a natural number more than 1) equilibriumvoltages and n special charging voltages for charging n different kindsof secondary batteries, each of the equilibrium voltage equalingelectromotive force of the secondary battery in a fully chargedcondition, and each of the special charging voltages supplying thesecondary battery with charging electric current of peak or almost peakvalue, wherein each of the special charging voltages is larger than thecorresponding equilibrium voltage and does not reach a region of voltagecausing irreversible chemical reaction in the corresponding secondarybattery; and

charging a secondary battery by first to eighth steps, the first step ofinitializing a counter variable k (k=1,2, . . . ,n) to 1;

the second step of applying the kth smallest special charging voltage ofthe n special charging voltages to the secondary battery for apredetermined time;

the third step of jumping to the sixth step if k is equal to n;

the fourth step of detecting voltage applied to the secondary batterywhile applying the kth smallest special charging voltage to thesecondary battery for the predetermined time;

the fifth step of incrementing k by 1 and returning to the second stepif the detected voltage is larger than the kth smallest special chargingvoltage; otherwise passing to the sixth step;

the sixth step of switching voltage applied to the secondary batteryfrom the kth smallest special charging voltage to the kth smallestequilibrium voltage of the n equilibrium voltages; and

the seventh step of detecting electric current flowing through thesecondary battery while applying the kth smallest equilibrium voltage tothe secondary battery for a short time; and

the eighth step of returning to the second step and iterating the abovesteps if the detected electric current is larger than standard electriccurrent for finishing charging; otherwise, halting charge of thesecondary battery.

The charging method of the second aspect has the same effect as that ofthe first aspect. Additionally the charging method of the second aspectautomatically identifies the kind of secondary battery in the process ofcharging so as to rapidly and appropriately charge electricity to thekind of secondary battery basing on the selected equilibrium voltage andspecial charging voltage without overcharging and causing excessivechemical reaction (oxidation-reduction reaction) in the secondarybattery until the kind of secondary battery is fully charged.

A third aspect of a charging method for a secondary battery according tothe present invention comprises:

previously storing n (n is a natural number more than 1) equilibriumvoltages and n special charging voltages for charging n different kindsof secondary batteries, each of the equilibrium voltages equalingelectromotive force of the secondary battery in a fully chargedcondition, and each of the special charging voltages supplying thesecondary battery with charging electric current of peak or almost peakvalue, wherein each of the special charging voltages is larger than thecorresponding equilibrium voltage and does not reach a region of voltagecausing irreversible chemical reaction in the corresponding secondarybattery; and

charging a secondary battery according to first to eighth steps, thefirst step of initializing a counter variable k (k=1,2, . . . ,n) to 1;

the second step of applying the kth smallest special charging voltage ofthe n special charging voltages to the secondary battery for apredetermined time;

the third step of jumping to the sixth step if k is equal to n;

the fourth step of detecting voltage applied to the secondary batterywhile applying the kth smallest special charging voltage to thesecondary battery for the predetermined time;

the fifth step of passing to the sixth step if the voltage detection isthe first time or a voltage difference between present and past voltagesdetected during application of the kth smallest special charging voltageis within a preset range; otherwise, incrementing k by 1 and returningto the second step;

the sixth step of switching voltage applied to the secondary batteryfrom the kth smallest special charging voltage to the kth smallestequilibrium voltage of the n equilibrium voltages; and

the seventh step of detecting electric current flowing through thesecondary battery while applying charging voltage of the kth smallestequilibrium voltage to the secondary battery for a short time; and

the eighth step of returning to the second step and iterating the abovesteps if the detected electric current is larger than standard electriccurrent for finishing charging; otherwise, halting charge of thesecondary battery.

The charging method of the third aspect also has the same effect as thatof the first aspect. Additionally the charging method of the secondaspect automatically identifies the kind of secondary battery in theprocess of charging so as to rapidly and appropriately chargeelectricity to the kind of secondary battery basing on the selectedequilibrium voltage and special charging voltage without overchargingand causing excessive chemical reaction (oxidation-reduction reaction)in the secondary battery until the kind of secondary battery is fullycharged.

A fourth aspect of a charging method for a secondary battery accordingto the present invention comprises: observing voltage of the secondarybattery completed in charging; and recharging the secondary battery ifthe observed voltage is not larger than recharging voltage establishedto be smaller than equilibrium voltage equaling electromotive force ofthe secondary battery in a fully charged condition.

A secondary battery charged up by the charging method of the fourthaspect necessarily has effective voltage equal to or higher than therecharging voltage just when it is picked out from the chargingequipment, thereby being available.

Furthermore, by the method, a secondary battery is rechargedappropriately without causing excessive damaging chemical reaction(oxidation-reduction reaction) therein until it is fully charged,thereby remarkably increasing its effective battery cycles and reducingthe time to be fully charged.

A fifth aspect of a charging method for a secondary battery according tothe present invention comprises: repeating a charging operation cycleincluding check of a charged condition of the secondary battery andapplication of charging special charging voltage to the secondarybattery for a determined time, wherein a relaxation time is establishedbetween the charging operation cycles; and halting charging thesecondary battery when it is judged at the check that the secondarybattery is fully charged.

By the charging method of the fifth aspect, the relaxation timeestablished between the charging operation cycles leads accurate checkof the charged condition of a secondary battery in the next chargingoperation cycle thereof, thereby enhancing the reliability of charging.

A sixth aspect of a charging method for a plurality of secondarybatteries according to the present invention comprises: performing acharging turn as a series of the charging operation cycles each of whichis performed for each uncharged secondary battery, wherein the chargingoperation cycles are performed one by one for the respective secondarybatteries; repeating the charging turn for charging the plurality ofsecondary batteries, wherein the relaxation time is established betweenthe final charging operation cycle in one charging turn and the firstcharging operation cycle in the next charging turn; and halting chargeof each secondary battery when it is judged at the check that thesecondary battery is fully charged.

By the charging method of the sixth aspect, charging is stopped for therelaxation time between the charging operation cycle in one chargingturn and the first charging operation cycle in the next charging turn,so as to bring a surface of an electrode of the secondary battery into astable condition, thereby accurately checking the charged condition ofthe secondary battery in the nest charging turn so as to decide whetherthe secondary battery is fully charged or not.

Complementarily speaking, in the process of charging a secondarybattery, electrode reaction occurs on an electrode surface touchingelectrolyte. In this electrode reaction are simultaneously performedmovement of reactant to the electrode surface from the electrolyte,movement of electron between the reactant and the electrode, andmovement of product into the electrolyte from the electrode surface. Ittakes quite a long time for these movements so that the secondarybattery, if the charged state thereof is checked immediately afterpausing charge of the secondary battery, may be misread as if it reachedthe fully charged condition because of ion and the like beingelectrophoresed around the electrode surface. The relaxation time isadvantageous for preventing such misreading. By the charging method ofthe sixth aspect, the relaxation time as a partial process in a cycle ofcharging each of secondary batteries is established rationally andeffectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a charging equipment for a secondarybattery 1 according to any of first to seventh embodiments of thepresent invention.

FIG. 2 is a circuit diagram for detecting electromotive force of asecondary battery 1.

FIG. 3 illustrates current-voltage graphs of a secondary battery 1 indifferent charging rates.

FIG. 4 is a graph showing a relation of a necessary time for fullycharging a secondary battery 1 to electric current flowing therethrough.

FIG. 5 is a flow chart of charging control of a secondary battery 1 by acharging equipment according to a first embodiment of the presentinvention.

FIG. 6 is a circuit diagram for switching voltage applied to a secondarybattery 1 according to the first embodiment.

FIG. 7 is a time chart showing timings of switching voltage applied to asecondary battery 1 according to the first embodiment.

FIG. 8 is a time chart showing variation of voltage applied to asecondary battery 1 in association with switching voltage applied to thesecondary battery 1 according to the first embodiment.

FIG. 9 is a time chart about the battery terminal voltage, the chargingelectric current, and the check electric current of a nickel-hydrogenbattery.

FIG. 10 is a time chart about the battery terminal voltage, the chargingelectric current, and the check electric current of a nickel-cadmiumbattery.

FIG. 11 is a flow chart of charging control of a secondary battery 1 bya charging equipment according to a second embodiment of the presentinvention.

FIG. 12 is a flow chart of charging control of a secondary battery 1 bythe charging equipment according to the second embodiment.

FIG. 13 is a flow chart of charging control of a secondary battery 1 bythe charging equipment according to the third embodiment.

FIG. 14 is a flow chart of charging control of a secondary battery 1 bythe charging equipment according to the third embodiment.

FIG. 15 is a graph showing a relation of voltage difference ΔE_(s),which equals special charging voltage E_(s) minus open-circuit voltageE_(x) of a secondary battery 1, to the necessary time for fullycharging.

FIG. 16 is a flow chart of charging control of a secondary battery 1 bya charging equipment according to a fourth embodiment of the presentinvention.

FIG. 17 is a flow chart of charging control of a secondary battery 1 bya charging equipment according to a fifth embodiment of the presentinvention.

FIG. 18 is a flow chart of charging control of a secondary battery 1 bya charging equipment according to a sixth embodiment of the presentinvention.

FIG. 19 is a flow chart of charging control of a secondary battery 1 bya charging equipment according to a seventh embodiment of the presentinvention.

FIG. 20 is a block diagram of a charging equipment for a secondarybattery 1 according to an eighth embodiment or a ninth embodiment of thepresent invention.

FIG. 21 is a flow chart of charging control of a secondary battery 1 bythe charging equipment according to the eighth embodiment.

FIG. 22 is a flow chart of charging control of a secondary battery 1 bythe charging equipment according to the ninth embodiment.

FIG. 23 is a basic circuit diagram of the charging equipment accordingto the eighth embodiment or the ninth embodiment.

FIG. 24 is a block diagram of the charging equipment for a plurality ofsecondary batteries 1 according to a tenth embodiment or an eleventhembodiment of the present invention.

FIG. 25 is a flow chart of charging control of a plurality of secondarybatteries 1 by the charging equipment according to the tenth embodiment.

FIG. 26 is a flow chart of charging control of a plurality of secondarybatteries 1 by the charging equipment according to the eleventhembodiment.

FIG. 27 is a block diagram of a charging equipment for a plurality ofsecondary batteries 1 according to a twelfth embodiment of the presentinvention.

FIG. 28 is a flow chart of charging control of a plurality of secondarybatteries 1 by the charging equipment according to the twelfthembodiment.

FIG. 29 is a plan view of a charging equipment for a plurality ofsecondary batteries 1 according to a fourteenth embodiment of thepresent invention.

FIG. 30 is a sectional side view of a charging equipment for a pluralityof secondary batteries 1 according to a fifteenth embodiment of thepresent invention.

FIG. 31 is a sectional rear view of take-off means of a chargingequipment for a plurality of secondary batteries 1 according to asixteenth embodiment of the present invention.

FIG. 32 is a sectional side view of take-off means of a chargingequipment for a plurality of secondary batteries 1 according to aseventeenth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A charging method by the charging equipment for a secondary battery inthe present invention explained below is characterized in that highelectric current is supplied to a secondary battery by applying thehighest voltage (a predetermined charging voltage) out of a region ofcharging voltage causing irreversible chemical reaction in the secondarybattery so as not to damage the internal structure of the secondarybattery, and that the secondary battery is periodically checked whetherthe secondary battery is fully charged or not (whether charge of thesecondary battery is finished or not). For this check, equilibriumcharging voltage for equilibrium cell potential of the secondary batteryin a fully charged condition is applied to facilitate quick and accuratejudge whether the secondary battery precisely is fully charged or not.By this charging method, the time for fully charging a secondary batterycan be reduced to thirty minutes or less. Furthermore, by the method,electricity can be appropriately charged to the secondary batteryappropriately without causing excessive damaging chemical reaction(oxidation-reduction reaction) in the secondary battery till thesecondary battery is fully charged, thereby increasing effective batterycycles of the secondary battery to five thousands times or more.

First of all, a fundamental composition of a charging equipment for asecondary battery according to the present invention will be explainedreferring to FIG. 1.

The charging equipment shown in FIG. 1 is provided for charging asecondary battery 1. The charging equipment comprises a power supplypart 2, a current detection part 3, a voltage detection part 9, and acontrol part 4 for programming and calculating. The power supply part 2includes a transformer-rectifier circuit for changing commercialalternating current into direct current. The current detection part 3detects a value of charting electric current flowing through thesecondary battery 1. The voltage detection part 9 detects a value ofvoltage applied in the secondary battery 1, or a value of chargingvoltage supplied to the secondary battery 1. The control part 4 ischarge control means for controlling charge of the secondary battery 1.The value of electric current detected by the current detection part 3and the value of voltage detected by the voltage detection part 9 aretransmitted to the control part 4.

The control part 4 serving as the charge control means comprises astorage means (memory), which previously stores two values of chargingvoltage: equilibrium voltage E_(eq) provided for equilibrium cellvoltage of the secondary battery 1 in a fully charged condition (seeFIG. 3) and special voltage E_(s) larger than the equilibrium voltageE_(eq) (as showing FIG. 3, the special charging voltage E_(s)corresponds to the peak value of electric current I_(so) which isreached when charging current is not increased any more. When thesecondary battery 1 whose charging rate is almost 0% is charged, theincreasing rate of charging current to increasing applied voltage (ΔIΔE) is decreased just before the charging current reaches the peakvalue. The special charging voltage E_(s) relative to electric currentdoes not reach a region thereof causing irreversible chemical reaction(an irreversible chemical reaction D).

The control part 4 also stores several programs such as a judgingprogram for judging whether the secondary battery 1 is fully charged ornot, and a charge time predicting program for estimating necessary timet to fully charge the secondary battery.

A reference numeral 5 in FIG. 1 designates a voltage/electric currentcontrol part, which controls change of voltage and electric currentflowing through the secondary battery 1 according to a command from thecontrol part 4. In other words, the voltage/electric current controlpart 5 comprises a switching means for switching charging voltagebetween the equilibrium voltage E_(eq) and the special voltage E_(s).

A reference numeral 6 designates a charging voltage supply part, whichsupplies the charging voltage set by the voltage/electric currentcontrol part 5 according to a starting command, and finishes chargingaccording to an ending command from the control part 4. A referencenumeral 7 designates a display part for displaying a necessary time t tofully charge the secondary battery 1, and others, which are calculatedin the control part 4. A reference numeral 8 designates an operationpart, which is operated by a user for starting and the like.

As for the following embodiments, the charging equipment comprises thedisplay part 7 as a visual monitor for indicating the necessary time tto fully charge the secondary battery 1 and others to a user. However,instead of the visual type display part 7, the charging equipment mayhave any type monitor device using sound etc.

A herein-said secondary battery means a rechargeable battery, which canrepeat charge-discharge cycles. In the charging process, electricalenergy is transformed into chemical potential energy, which is stored inthe secondary battery. The stored chemical potential energy is convertedback into electrical energy when the need arises.

Typical and practical batteries serving as the secondary battery 1 are anickel-cadmium battery, a nickel metal hydride battery, a lithium ionbattery, a NAS battery, and the like.

A nickel-cadmium battery serving as the secondary battery 1 charged bythe charging equipment of each embodiment will now be explained.

A nickel-cadmium battery is a storage battery which comprises ahermetically sealed cell container filled with alkali electrolyte, aseparator made of synthetic resins for separating the cell containerinto two rooms, a positive electrode made of nickel oxyhydroxide(Ni(OOH)) in one room, and a negative electrode made of cadmium (Cd) inthe other room.

The electrolyte is an aqueous solution whose main ingredient ispotassium hydroxide with high electric conductivity. If needed, lithiumhydroxide, sodium hydroxide, etc. may be added to this aqueous solutionin order to raise the capacity of the positive electrode.

In electromotive reaction of the nickel-cadmium battery, the chemicalreaction on the positive electrode is expressed by the followingformula.

The chemical reaction on the negative electrode is expressed by thefollowing formula.

In its discharging process, oxyhydroxide (Ni(OOH)) reacts with water(H₂O) and electron (e⁻) from the positive electrode to formhydroxylation nickel (Ni(OH)₂) on the positive electrode.

On the other hand, cadmium (Cd) reacts with hydroxylation ion (OH⁻)generated from the positive electrode and entering the negativeelectrode room through the separator to form hydroxylation cadmium(Cd(OH)₂) and electron (e⁻) on the negative electrode. This electron(e⁻) passes through external load and is supplied to the positiveelectrode.

In this cycle, the electron (e⁻) passing through the external load isused for work. Therefore, this cycle requires the following conditionsfor its smooth performance: Plenty of water (H₂O) involvinghydroxylation nickel (Ni(OH)₂) as production in low concentration existsaround the positive electrode, and hydroxylation cadmium (Cd(OH)₂) inlow concentration around the negative electrode. This relation can beexpressed by the following formula.E _(emf) =E ⁰+((R*T)F)*ln(C _(aq)(C _(N) *C _(C)))

E⁰ is standard electromotive force. E⁰ is a constant decided accordingto materials of the positive and negative electrodes regardless ofquantity of the substances. For example, the standard electromotiveforce E⁰ of the nickel-cadmium battery is about 1.2V(Volt). R is the gasconstant, T is absolute temperature, and F is Faraday constant.

The above-mentioned formula shows that, at the positive electrode, thehigher the concentration (C_(aq)) of water (H₂O) is and the lower theconcentration (C_(N)) of hydroxylation nickel (Ni(OH)₂) is, the largerthe Electromotive force E_(emf) becomes, and at the negative electrode,the lower the concentration (C_(c)) of hydroxylation cadmium (Cd(OH)₂)is, the larger the electromotive force E_(emf) becomes. It means thatthe larger the electromotive force E_(emf) is, the larger the capacityof accumulation of electricity in the secondary battery becomes.

Incidentally, a circuit shown in FIG. 2 may be made so as to know thecharged condition of the secondary battery 1 exactly. In the circuit, avariable power supply 11 is connected to the secondary battery 1, and anelectrical potential of the variable power supply 11 is adjusted to apotential equaling the electromotive force E of the secondary battery 1.That is, the variable power supply 11 is adjusted so that a value of theelectric current detected by the current detection part 3 may be set to±0 mA, whereby the electromotive force E_(emf) of the secondary battery1 is measured indirectly. In this way, for charging various types ofsecondary batteries 1, the electromotive force E_(emf) of each of thesecondary batteries 1 in their fully charged condition is previouslyinputted into the control part 4 serving as the storage means.

Next, referring to the graph of FIG. 3, a characteristic of relationbetween voltage and current for charging the secondary battery 1 will beexplained, which is a fundamental theory underling hereinafterdescription of the present charging method.

FIG. 3 shows voltage-current characteristic curves in a chargedsecondary battery 1 corresponding to different charging rates, withbattery terminal voltage (applied voltage) as the abscissa, and chargingcurrent as the y-axis.

A graph α drawn in a dashed line expresses a voltage-currentcharacteristic during charge of the secondary battery 1 when itscharging rate is approximately 0%. In this case, even if the voltageE_(α) lower than the standard voltage (nominal voltage) E⁰ is applied,electric current starts flowing to be charged. (The applied voltage(battery terminal voltage) when electric current begins flowing to becharged is defined as open-circuit voltage.)

The larger the charging rate is, the higher the open-circuit voltagebecomes. A graph β drawn with a long dashed short dashed line in FIG. 3expresses a voltage-current characteristic during charge of thesecondary battery 1 when its charging rate is approximately 50%.Open-circuit voltage E_(β) for starting flow of electric current to becharged is applied higher than the open-circuit voltage E_(α) forcharging the secondary battery 1 when its charging rate is approximately0%. A graph γ drawn in a long dashed double-short dashed line in FIG. 3expresses a voltage-current characteristic during charge of thesecondary battery 1 when its charging rate is approximately 90%,requiring open-circuit voltage E_(γ) higher than E_(β). A graph δ drawnin a continuous line in FIG. 3 expresses a voltage-currentcharacteristic during charge of the secondary battery 1 when itscharging rate is approximately (less than) 100%, requiring open-circuitvoltage E_(δ) higher than E_(γ). Open-circuit voltage for the secondarybattery 1 when its charging rate is just 100% is equal to theequilibrium voltage E_(eq) which is higher than E_(δ).

Electric current charged in the secondary battery 1 is increasedsubstantially in proportion to increase of applied voltage higher thanopen-circuit voltage E E_(α), E_(β), E_(γ), E_(δ) etc. corresponding toits initial charging rate. When the applied voltage passes over acertain voltage (an inflection point of the voltage-current curve), theincrease rate of charging electric current to applied voltage (ΔI ΔE)begins to decrease. Finally, charging electric current reaches peakelectric current I_(so) and does not increase any more even if appliedvoltage is increased.

Applied voltage corresponding to the peak electric current I_(so), whichis charging electric current when the increase rate of charging electriccurrent to applied voltage (ΔI ΔE) becomes zero, is the special voltageE_(s) peculiar to each secondary battery 1, determined by a kind, adegraded state, and other element of the secondary battery 1 to becharged.

If voltage higher than the special voltage E_(s) is applied to thesecondary battery 1, oxidation-reduction reaction of active substance isfurther promoted so as to cause electrolysis reaction in the secondarybattery 1, whereby the characteristic of negative resistance appears. Inthe worst case, the internal structure of the secondary battery 1 may bedestroyed by unexpected abnormalities such as exothermic reaction andswelling reaction. Even if such the worst case does not happen, appliedvoltage higher than the special voltage E_(s) promotes irreversiblechemical reaction leading to reduction of effective battery cycles ofthe secondary battery 1. The irreversible chemical reaction region Dhatched in FIG. 3 is a region of the relationship between chargingelectric current and applied voltage such as to cause irreversiblechemical reaction which is harmful to the secondary battery 1.

The graph α corresponding to the secondary battery 1 when its chargingrate is approximately 0% shows that the charged peak electric currentI_(so) is still kept in spite of increasing applied voltage in theregion D. Each of the graphs β, γ and δ shows that, in the region D, asapplied voltage is increased, charging electric current is decreased andthe decreasing rate of charging electric current is increased. Finally,the characteristic of negative resistance of the secondary battery 1 inthe region D, which appears as the irreversible chemical reaction, isturned as the bulk specific resistance increasing in proportion to therise of applied voltage.

Therefore, it is necessary for charging a secondary battery 1 to controlvoltage applied to the secondary battery 1 lest the charging electriccurrent relative to applied voltage should enter the irreversiblechemical reaction region D before the secondary battery 1 is fullycharged (the state of its charging rate 100%).

Incidentally, FIG. 3 shows that the minimum voltage in the irreversiblechemical reaction region D (on the border of the reaction region D)becomes smaller according to increase of charging rate (or decrease ofcharging electric current). The capacity of accumulation of electricityin the secondary battery 1 is product of charging electric currentmultiplied by charge time. Therefore, for shortening the charge time, itis necessary to increase charging electric current. Under the constantcharging rate, the higher applied voltage is, the larger chargingelectric current becomes.

The requirement for charging a secondary battery 1 is to prevent therelationship between charging electric current and applied voltage fromentering the region D in spite of increase of charging rate till thesecondary battery 1 is fully charged, and to flow the maximum electriccurrent in the secondary battery when its charging rate is approximately0%. Taking the requirement into account, the open-circuit voltage E_(eq)for the fully charged secondary battery 1, shown in FIG. 3, is worthy ofapplication to the secondary battery 1. The voltage E_(eq) is used asthe equilibrium voltage provided for equilibrium cell potential of thesecondary battery 1 in its fully charged condition.

The application of equilibrium voltage E_(eq) facilitates easy judgmentwhether the secondary battery 1 is fully charged or not, because thehigher charging rate is, the lower charging electric current becomes.

This merit will be explained referring to the FIG. 3. When theequilibrium voltage E_(eq) is constantly applied to the terminals of thesecondary battery 1 whose initial charging rate is approximately 0%,charging electric current I_(eqo) (see the graph α) flows through thesecondary battery 1 at first. The higher its charging rate risesaccording to the progress of charge, the lower charging electric currentfalls from the electric current I_(eqo) (see the graphs β and γ). Therelative value of the charging electric current to the applied voltagedoes not enter the irreversible chemical reaction region D until thesecondary battery 1 is fully charged (its charging rate reaches 100%).The charging electric current becomes 0 mA when the secondary battery 1is fully charged. Thus, whether the secondary battery 1 is fully chargedor not can be easily judged.

However, the secondary battery 1 has the potential for receiving thepeak electric current I_(so) higher than the electric current I_(eqo)without causing irreversible chemical reaction in the secondary battery1, while the special charging voltage E_(s) in spite of any chargingrate of the secondary battery 1 (whether charging rate of the secondarybattery 1 is approximately 0% or 100%). Such high charging electriccurrent flowing through the secondary battery 1 can remarkably reducecharge time in comparison with the charge time when the secondarybattery 1 is charged by application of the equilibrium voltage E_(eq).

Therefore, according to the present embodiment, the secondary battery 1is charged by constantly applying the special charging voltage E_(s) fora considerable time so as to flow the maximum charging electric current(the peak electric current I_(so)) out of the irreversible chemicalreaction region D, and by switching applied voltage from the specialcharging voltage E_(s) to the equilibrium voltage E_(eq) at a suitabletime so as to reduce charging electric current. Whether the secondarybattery 1 is fully charged or not is judged during the application ofthe equilibrium voltage E_(eq) to the secondary battery 1.

While the special charging voltage is applied to the secondary battery 1so as to increase the charging rate thereof, almost the peak electriccurrent I_(so) is kept as charging electric current, thereby increasingthe charging rate for a greatly short time. By applying the equilibriumvoltage E_(eq) to the secondary battery 1 for a suitable time, chargingelectric current becomes lower according to increase of charging rate ofthe secondary battery 1, thereby preventing the secondary battery 1 fromovercharging and facilitating easy judgment whether the secondarybattery 1 is fully charged or not.

Voltage to be applied for charging the secondary battery 1 with largeelectric current is not limited to the special charging voltage E_(s)corresponding to the peak electric current I_(so). It may be lower thanthe voltage E_(s) so as to correspond to electric current smaller thanthe peak electric current I_(so). In other words, as shown in FIG. 3,the voltage to be applied is set to a value corresponding to a selectivevalue of electric current, out of the irreversible chemical reactionregion D, which extremely approaches but does not reach the peakcurrent. The selective value of electric current is pointed on thecurrent-voltage graph where the increasing rate of charging electriccurrent to applied voltage (ΔI ΔE) reduces. By applying this voltage,the secondary battery 1 can be also charged with high electric current,which is almost the peak electric current I_(SO).

To provide the peak electric current I_(so), which is kept constantregardless of variation of charging rate, for charging the secondarybattery 1, the special charging voltage E_(s) corresponding to the kindof secondary battery 1 to be charged may be established basing on thegraph a in FIG. 3, for example, i.e., the current-voltage characteristicof the secondary battery 1 whose charging rate is almost 0%, wherein thepeak electric current I_(so) is kept in a certain variation area ofapplied voltage. In other words, the special charging voltage E_(s) isset to voltage just before reaching the irreversible chemical reactionregion D, which is defined on the graph as a point where the increasingrate of charging electric current according to the rise of appliedvoltage (ΔI ΔE) is decreased to 0 or almost 0.

FIRST EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the firstembodiment will be explained.

This charging equipment uses the method comprising the step of:switching charge with high electric current to charge with applicationof the equilibrium voltage at a suitable time, and judging basing on thedetected value of electric current which is suitable, charge with highelectric current or charge with application of the equilibrium voltage.

FIG. 1 shows composition of the charging equipment of the firstembodiment. The control part 4 has a check current judging program forjudging whether check current i detected by the current detection part 3during application of the equilibrium voltage E_(eq) to the secondarybattery 1 is larger than a preset standard electric current J forfinishing charging or not, a charge time predicting program forestimating necessary time t to fully charge the secondary battery 1basing on the value of check current i detected by the current detectionpart 3 during application of the equilibrium voltage E_(eq). In short,the control part 4 functions as both of a check current judging meansand a charge time predicting means.

The charging equipment of the first embodiment is controlled by thiscontrol part 4 as follows. The charging equipment applies the specialcharging voltage E_(s) (or voltage considerably smaller than the specialcharging voltage E_(s)) to the secondary battery 1 for a determined timeT₁. After charge with high electric current during the application ofthe special charging voltage E_(s), the charging equipment switchesvoltage applied to the secondary battery 1 from the special chargingvoltage E_(s) to the equilibrium voltage E_(eq) and detects a value ofelectric current i flowing through the secondary battery 1 during theapplication of the equilibrium voltage E_(eq) to the secondary battery1. Basing on the detected value of electric current i, the chargingequipment predicts necessary time t to fully charge the secondarybattery 1 and displays necessary time t on the display part 7 with LED,LCD or the like, and simultaneously; the storage means in the controlpart 4 [step A1].

Both the special charging voltage E_(s) and the equilibrium voltageE_(eq) are determined by the kind or type of secondary battery 1, suchas the nickel-cadmium battery, the nickel metal hydride battery, and thelithium ion battery. For example, with regard to the nickel-cadmiumbattery, the equilibrium voltage E_(eq) is set to around 1.41 V, and thespecial charging voltage E_(s) is set to around 1.81 V higher than theequilibrium voltage E_(eq).

A user manipulates the operation part 8 to start charging [step A2],whereby the charging equipment applies the selected special chargingvoltage E_(s) to the secondary battery 1 for a predetermined to,e (afixed time) T₁ [step A3].

The predetermined time T₁ is calculated basing on variation of chargingelectric current according to the time progress during the applicationof special charging voltage E_(s). After the predetermined time T₁passes, the charging equipment short-circuits the secondary battery 1between its terminals for an extremely short time T₂ [step A4], so as toremove electric charge from the electrode interface of the secondarybattery 1. Then, the charging equipment switches applied voltage to theequilibrium voltage E_(eq) [step A5].

The charging equipment detects a value of electric current i flowingthrough the secondary battery 1 during the application of equilibriumvoltage E_(eq) to the secondary battery 1 of short duration [step A6].

Next, the charge time predicting program calculates the necessary time tto fully charge the secondary battery 1 basing on the detected electriccurrent i, that is, the time t required for the detected electriccurrent i to reach the standard electric current J for finishingcharging (the value of electric current which will be detected at thefully charged condition), and this necessary time t is indicated on thedisplay part 7 [step A7].

At the same time, the check current judging program compares thedetected electric current i with the standard electric current J forfinishing charging [step A8]. If the detected electric current i islarger than the standard electric current J for finishing charging, thecontrol step returns to the step A3, and the above steps (chargecontrol) are repeated. Otherwise, the charging equipment recognizes thatthe secondary battery 1 is fully charged, and it stops charging thesecondary battery 1 [step A9].

Incidentally, if equilibrium voltage E_(eq) is applied and the chargingrate is 100% (the charging equipment judges whether the detected valueof electric current i is larger than the preset standard value ofelectric current J for finishing charging or not. If the detected valueof electric current i is larger than the standard value of electriccurrent J for finishing charging, the charging equipment applies thespecial charging voltage E_(s) to the secondary battery 1 again;otherwise, charge of the secondary battery 1 is halted.

Incidentally, the necessary time t to fully charge the secondary battery1 can be predicted from the graph in FIG. 4, for example, whichillustrates the relation between electric current i and the necessarytime t.

The graph in FIG. 4 shows the relation between the detected value ofelectric current i during application of the equilibrium voltage E_(eq)and the necessary time t till the secondary battery 1 is fully charged.The necessary time t is a time required by electric current i detectedby the current detection part 3 to reach the standard value of electriccurrent J for finishing charging, e.g., 0 mA.

Referring to FIG. 3, electric current I_(eqo) is detected as a value ofelectric current i during application of the equilibrium voltage E_(eq)to the secondary battery 1 whose charging rate is 0%. The graph in FIG.4 shows that, as the charging rate is increased, the necessary time tand the detected electric current i are decreased. In this graph, whenthe detected value of electric current i reaches 0 mA, the secondarybattery 1 is recognized to be fully charged so that the charging ratebecomes 100% and the necessary time t is 0 second.

Accordingly, if a conversion table for converting the check current iinto the necessary time t to fully charge the secondary battery 1 formedbasing on this graph, or a relational expression which formulates therelation between the check current i and the necessary time t to fullycharge the secondary battery 1 basing on the graph is made as the chargetime predicting program, the necessary time t to fully charge thesecondary battery 1 can be estimated basing on the detected value ofelectric current i.

Next, the control flow of charging the secondary battery 1 by thecharging equipment of the first embodiment will be explained referringto a flow chart shown in FIG. 5.

First of all, a user inputs a kind of secondary battery 1 to be chargedto the control part 4 by manipulating the operation part 8, therebyselecting the special charging voltage E_(s) and equilibrium voltageE_(eq) in correspondence to the kind of secondary battery 1 from a tablein the secondary battery 1 is fully charged), electric current itheoretically becomes 0 mA, as shown in the graphs in FIG. 3 and FIG. 4.However, the fact is that the electric current are slightly differentamong different secondary batteries of the same type. Therefore, thestandard electric current J for finishing charging to the value isdesired to be slightly more than 0 mA, such as 10 mA, for preventing thesecondary battery 1 from overcharging. In this case, the necessary timet to fully charge is a time required for the detected electric current ito reach a value not more than 10 mA.

The charging time T₁ for applying the special charging voltage E_(s)varies depending on the battery's capacity, structure, form, or thelike. For example, with regard to the nickel-cadmium battery, thecharging time T₁ is set to around 120 seconds. The extremely short timeT₂ for short-circuiting the terminals of the secondary battery 1 is atime required to clear the electric charge from the electrode interfaceof the secondary battery 1. With regard to the nickel-cadmium battery,the extremely short time T₂ is set to around 0.001 second. Furthermorethe short time T₃ for applying the equilibrium voltage E_(eq) is set toaround 0.1 second.

If the short time T₃ is set to more than 1 second, the above-mentionedstep A4 may be omitted.

To change charging voltage, shown in the flow chart of FIG. 5, thecircuit shown in FIG. 6 may be used, for example. Referring to FIG. 1, areference numeral 1 designates a secondary battery, a reference numeral3 designates a current detection part 3 for detecting charging electriccurrent flowing through the secondary battery 1, and a reference numeral9 designates a voltage detection part 9 for detecting voltage applied tothe secondary battery 1. This circuit has a first gate 36, a second gate37, and a third gate 38 for switching elements such as field-effecttransistor (FET). A reference numeral 31 designates a first power supply(variable power supply) that can change the setting of equilibriumvoltage E_(eq) suitable for a kind or a type of the secondary battery 1to be charged, and a reference numeral 32 designates a second powersupply for applying the special charging voltage E_(s).

For further details, the plus terminal of the secondary battery 1 isconnected to the emitter of the first gate 36, the emitter of the secondgate 37, the collector of the third gate 38, and the minus terminal ofthe voltage detection part 9, respectively. The collector of the firstgate 36 is connected to the plus terminal of the second power supply 32,and the minus terminal of the second power supply 32 is connected toboth the plus terminal of the first power supply 31 and the collector ofthe second gate 37. The minus terminal of the first power supply 31 isconnected to the plus terminal of the current detection part 3. Theminus terminal of the current detection part 3 is connected to the plusterminal of the voltage detection part 9, the minus terminal of thesecondary battery 1, and the emitter of the third gate 38.

Next, the method for controlling applying voltage to the secondarybattery 1 using the circuit in FIG. 6 will be explained referring toFIG. 7 and FIG. 8.

First of all, only the first gate 36 is switched on so as to apply thespecial charging voltage E_(s) to the secondary battery 1 for adetermined time T₁. After the passage of the determined time T₁, thefirst gate 36 is switched off and only the third gate 38 is switched onso as to short-circuit the terminals of the secondary battery 1 for anextremely short time T₂. In this way, the gates 36, 37 and 38 constitutemeans for short-circuiting the secondary battery 1 between itsterminals. By the short-circuiting, electric charge is removed from theelectrode interface of the secondary battery 1 so as to enable voltageto be smoothly applied to the secondary battery 1 at the next step, andto stabilize electric current flowing through the secondary battery 1immediately after change of charging voltage, thereby ensuring accuratedetection of electric current.

After the passage of the extremely short time T₂, the third gate 38 isswitched off and the second gate 37 is switched on so as to apply theequilibrium voltage E_(eq) for checking the charged condition of thesecondary battery 1 for a short time T₃. During the short time T₃, thecurrent detection part 3 detects a value of electric current i flowingthrough the secondary battery 1. Basing on the detected electric currenti, the check current judging program judges whether the secondarybattery 1 is fully charged or not, and the charge time predictingprogram calculates the necessary time t to fully charge the secondarybattery 1. After the short time T₃ passes, the second gate 37 isswitched off.

If the check current judging program judges that the secondary battery 1is not fully charged, the first gate 36 is switched on so as to applythe special charging voltage E_(s) for charging the secondary battery 1,and above-mentioned control steps are repeated.

On the other hand, if the check current judging program judges that thesecondary battery 1 is fully charged, charge of the secondary battery 1is halted.

According to the charging equipment of the first embodiment, a value ofelectric current i is detected so as to check the charged condition ofthe secondary battery 1 periodically, thereby appropriately charging thesecondary battery 1 without causing excessive damaging chemical reaction(oxidation-reduction reaction) in the secondary battery 1 till thesecondary battery 1 is fully charged. The internal structure of thesecondary battery 1 is prevented from being damaged so as to remarkablyincrease effective battery cycles of the secondary battery 1. Moreover,by this charging method with the charging equipment of the firstembodiment, the special charging voltage E_(s) larger than theequilibrium voltage E_(eq) is mainly applied so as to make considerablyhigh charging electric current flow through the secondary battery 1,thereby reducing charging time.

Moreover, the charging equipment of the first embodiment estimatesnecessary time t to fully charge the secondary battery 1 basing on thedetected electric current i, and displays the necessary time t on thedisplay part 7, thereby improving users' convenience for monitoring thetime required to fully charge the secondary battery 1.

Furthermore, the charging equipment of the first embodimentshort-circuits the terminals of the secondary battery 1 before itswitches voltage applied to the secondary battery 1 from the specialcharging voltage E_(s) to the equilibrium voltage E_(eq). By theshort-circuiting, electric charge is cleared from the electrodeinterface of the secondary battery 1 so as to enable voltage applied tothe secondary battery 1 to be smoothly switched to the equilibriumvoltage E_(eq), thereby stabilizing electric current flowing through thesecondary battery 1 immediately after the change of voltage to theequilibrium voltage E_(eq). Consequently, the charging equipment candetect electric current i accurately, and charge the secondary battery 1appropriately.

SECOND EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

Next, a charging equipment for a secondary battery 1 according to thesecond embodiment of the present invention will be explained.

The charging equipment of the second embodiment is characterized in thatit can identify the kind of secondary battery 1 automatically in theprocess of charge without inputting data of the kind of secondarybattery 1 so as to charge the secondary battery 1 rapidly till it isfully charged. The “kind” of secondary battery 1 means not onlyclassification of the secondary batteries by the difference in substanceof the plus terminal and/or the minus terminal such as a nickel-cadmiumbattery and a nickel-hydrogen battery, but also classification of thesecondary battery having the same plus terminal and the same minusterminal by the difference in charge capacity.

The equilibrium voltage E_(eq) and the special charging voltage E_(s)are determined by the sort and the charge capacity of the secondarybattery.

For example, regarding a nickel-cadmium battery whose charge capacity is1000 mAh(milliampere-hour), the equilibrium voltage is about 1.41V, andthe special charging voltage is about 1.80V. Regarding a nickel-hydrogenbattery whose charge capacity is 2000 mAh, the equilibrium voltage isabout 1.44V, and the special charging voltage is about 1.60V.

FIG. 9 is a time chart showing a time progress of the battery terminalvoltage, a time progress of charging electric current, and checkelectric current when a nickel-hydrogen battery is charged by thecharging equipment of the first embodiment under the condition that theequilibrium voltage is set to 1.44V and the special charging voltage isset to 1.60V, corresponding to the nickel-hydrogen battery. FIG. 10 is atime chart showing a time progress of the battery terminal voltage, atime progress of charging electric current, and check electric currentwhen a nickel-cadmium battery is charged by the charging equipment ofthe first embodiment under the condition that the equilibrium voltage isset to 1.44V and the special charging voltage is set to 1.60V,corresponding to the nickel-hydrogen battery. In both FIG. 9 and FIG.10, the determined time T₁ for applying the special charging voltage1.60V at the above-mentioned step A3 is set to 55 seconds, the processof short circuit at the step A4 is omitted, and the short time T₃ forapplying the equilibrium voltage 1.44V at the step A5 is set to 5seconds.

Between the power supply part 2 and the charging voltage supply part 6through the voltage/electric current control part 5, shown in FIG. 1,some resistance occurs so as to cause voltage drop. When correspondingto the nickel-hydrogen battery, the charging equipment is designed sothat voltage of 2.0V from the power supply part 2 drops while passingthe voltage/electric current control part 5 and the charging voltagesupply part 6 so as to set the voltage applied between the terminals ofthe nickel-hydrogen battery to about 1.6V.

As shown in FIG. 3, while applying special charging voltage E_(s) to thesecondary battery 1, constant charging electric current (that is thepeak electric current I_(so)) flows through the secondary battery 1regardless of variation of its charging rate. If voltage lower than thespecial charging voltage E_(s) is applied to the secondary battery 1,charging electric current flowing through the secondary battery 1 isdecreased according to increase of the charging rate.

According to such characteristics, as shown in FIG. 9, when anickel-hydrogen battery is charged with the setting voltage matchingwith the nickel-hydrogen battery, the voltage applied between theterminals of the nickel-hydrogen battery is about 1.6V corresponding tothe special charging voltage (1.60V) of the nickel-hydrogen battery, andthe constant electric current (the peak value of electric currentI_(so)) corresponding to the special charging voltage flows through thenickel-hydrogen battery, whereby the voltage drop between the powersupply part 2 and the charging voltage supply part 6 through thevoltage/electric current control part 5 is kept almost constant. That isto say, almost constant voltage without exceeding 1.6V is appliedbetween the terminals of the nickel-hydrogen battery and almost constantcharging electric current flows therethrough while charging from thebeginning of charge to the end of charge. The charging electric currentflowing through the nickel-hydrogen battery can be checked appropriatelyby periodically applying the suitable equilibrium voltage 1.44V to thenickel-hydrogen battery, thereby charging the nickel-hydrogen batteryrapidly and accurately till the fully charged condition.

As shown in FIG. 10, when a nickel-cadmium battery is charged withsetting of voltage corresponding to the nickel-hydrogen battery, thevoltage applied between the terminals of the nickel-cadmium batteryvaries between 1.4V and 1.6V for a while after starting charging.

This applied voltage is lower than the special charging voltage (1.80V)of the nickel-cadmium battery so that as its charging rate goes up,charging electric current flowing through it decreases gradually. Withthe diminution of charging electric current, voltage drop generatedbetween the power supply part 2 and the charging voltage supply part 6through the voltage/electric current control part 5 becomes smaller bydegrees, so that the voltage applied between the terminals of thenickel-cadmium battery becomes larger by degrees. Finally, the voltageexceeds 1.6V and reaches about 1.8V at the end of charge.

The charging electric current flowing through the nickel-cadmium batteryis checked by periodically applying the suitable equilibrium voltage1.44V to the nickel-cadmium battery. However, the equilibrium voltage1.44V corresponding to the nickel-hydrogen battery is higher than theequilibrium voltage 1.41V corresponding to the nickel-cadmium battery,so that the nickel-cadmium battery cannot be exactly charged till thefully charged condition.

To solve this problem, the charging equipment of the second embodimentdistinguishes a type of secondary battery to be charged between anickel-cadmium battery and a nickel-hydrogen battery, for example. Thecharging equipment applies voltage corresponding to the nickel-cadmiumbattery for charging a secondary battery 1 and for checking its chargingrate. If the charging voltage applied between the terminals of thesecondary battery 1 exceeds 1.6V, the secondary battery 1 is judged tobe a nickel-cadmium battery. Afterward, the charging equipment appliesvoltage corresponding to the nickel-cadmium battery for charging thesecondary battery 1 and for checking its charging rate.

The charging equipment of the second embodiment will be detailed. Thisis constructed similarly with that of FIG. 1. The storage means (memory)in the control part 4 stores equilibrium voltages E_(eq) and specialcharging voltages E_(s) corresponding to respective kinds of secondarybatteries. The control part 4 has a check current judging program and avoltage judging program. The check current judging program serves asmeans for judging whether electric current i detected by the currentdetection part 3 during application of the equilibrium voltage E_(eq) islarger than preset standard electric current J for finishing charging ornot. The voltage judging program serves as means for judging whethervoltage e detected by the voltage detection part 9 during application ofthe special charging voltage E_(s) is larger than the special chargingvoltage E_(s) or not.

Explanation of other parts in the charging equipment of the secondembodiment is omitted because they are almost similar with those of thefirst embodiment.

The control flow of charging the secondary battery 1 by the chargingequipment of the second embodiment, wherein the storage means in thecontrol part 4 stores two values of equilibrium voltage E_(eq) (E_(eql),E_(eqh)) and two values of special charging voltage E_(s) (E_(sl),E_(sh)) corresponding to two kinds of secondary batteries, referring tothe flow chart shown in FIG. 11.

The equilibrium voltage E_(eql) is lower than the equilibrium voltageE_(eqh) and the special charging voltage E_(s1) is lower than thespecial charging voltage E_(sh).

First of all, a user manipulates the operation part 8 of the chargingequipment to start charging [step B1]. Accordingly, the chargingequipment applies the lower special charging voltage E_(s1) to thesecondary battery 1 for a determined time (a fixed time) T₁ [step B2].

While the determined time T₁ of application of the lower specialcharging voltage E_(s1) to the secondary battery1, the voltage detectionpart 9 detects voltage e applied to the secondary battery 1 [step B3],and the voltage judging program judges basing on the detected value ofvoltage e [step B4]. If the detected voltage e is higher than the lowerspecial charging voltage E_(s1), the control step jumps to the latermentioned step B10 Otherwise, the control step goes to the next step B5.

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step B5] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage from the lower special chargingvoltage E_(s1) to the lower equilibrium voltage E_(ql), and applies thelower equilibrium voltage E_(eql) to the secondary battery 1 for a shorttime T₃ [step B6].

If the short time T₃ is set to more than 1 second, the above-mentionedstep B5 may be omitted.

The charging equipment detects a value of electric current i flowingthrough the secondary battery 1 during the application of the lowerequilibrium voltage E_(eq1) to the secondary battery 1 for a short timeT₃ [step B7].

Then, the check current judging program judges basing on the detectedvalue of electric current i [step B8]. If the detected electric currenti is larger than the standard electric current J for finishing charging,the control step returns to the step B2, and the above steps arerepeated. Otherwise, the charging equipment stops charging the secondarybattery 1 [step B9].

At the above mentioned step B4, if the voltage e detected by the voltagedetection part 9 is larger than the lower special charging voltageE_(s1), the charging equipment switches applied voltage from the lowerspecial charging voltage E_(s1) to the higher special charging voltageE_(sh), and applies the higher special charging voltage E_(s1) to thesecondary battery 1 for a determined time T₁ [step B10].

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step B11] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage from the higher special voltageE_(sh) to the higher equilibrium voltage E_(eqh), and applies the higherequilibrium voltage E_(eqh) to the secondary battery 1 for a short timeT₃ [step B12].

If the short time T₃ is set to more than 1 second, the above-mentionedstep B11 may be omitted.

The charging equipment detects a value of electric current i flowingthrough the secondary battery 1 during the application of the higherequilibrium voltage E_(eqh) to the secondary battery 1 for a short timeT₃ [step B13].

Then, the check current judging program judges basing on the detectedvalue of electric current i [step B14]. If the detected electric currenti is larger than the standard electric current J for finishing charging,the control step returns to the step B10, and the above steps arerepeated. Otherwise, the charging equipment stops charging the secondarybattery 1 [step B9].

The foregoing explanation has been given of charge control by thecharging equipment wherein the storage means in the control part 4stores two values of equilibrium voltage E_(eq1) and E_(eqh) and twovalues of special charging voltage E_(s1) and E_(sh) corresponding totwo kinds of secondary batteries.

The flow of charge control of the secondary battery 1 by the chargingequipment of the second embodiment, wherein the storage means in thecontrol part 4 stores n values of equilibrium voltage E_(eq) (E_(eq1),E_(eq2), . . . E_(eqn)) and n values of special charging voltage E_(s)(E_(s1), E_(s2), . . . E_(sn)) corresponding to respective n (n is anatural number more than 1) different kinds of secondary batteries, willbe explained referring to the flow chart shown in FIG. 12.

The voltages E_(eq1), E_(eq2), . . . E_(eqn) and the voltages E_(s1),E_(s2), . . . E_(sn) are ranked from the minimum to the maximum.

First of all, a counter variable k (k=1,2, . . . ,n) is initialized to 1[step C1]. A user manipulates the operation part 8 of the chargingequipment to start charging [step C2]. Accordingly, the kth smallestspecial charging voltage E_(sk) of the n special charging voltages isapplied to the secondary battery 1 set in the charging equipment for adetermined time (a fixed time) T₁ [step C3].

If the k is equal to n [step C4], the control step jumps to the belowmentioned step C8. If the k is not larger than n−1, the voltagedetection part 9 detects voltage e applied to the secondary battery 1while the determined time T₁ of applying the kth smallest specialcharging voltage E_(sk) to the secondary battery 1 [step C5], and thevoltage judging program judges basing on the detected voltage e [stepC6]. If the detected voltage e is larger than the kth smallest specialcharging voltage E_(sk), the rank of k increments by 1 [step C7], andthe control step returns to the step C3. Otherwise, the control stepgoes to the next step C8.

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step C8] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage from the kth smallest specialcharging voltage E_(sk) to the kth smallest equilibrium voltage E_(eqk),and applies the kth smallest equilibrium voltage E_(eq) k to thesecondary battery 1 for a short time T₃ [step C9].

If the short time T₃ is set to more than 1 second, the above-mentionedstep C8 may be omitted.

The charging equipment detects electric current i flowing through thesecondary battery 1 while the short time T₃ of applying the kth smallestequilibrium voltage E_(eqk) to the secondary battery 1 [step C10].

Then, the check current judging program judges basing on the detectedvalue of electric current i [step C11]. If the detected electric currenti is larger than the standard electric current J for finishing charging,the control step returns to the step C3, and the above steps arerepeated. Otherwise, the charging equipment stops charging the secondarybattery 1 [step C12].

As mentioned above, the charging equipment of the second embodiment hasthe same effect as that of the first embodiment. Additionally, thecharging equipment of the second embodiment automatically identifies thekind of secondary battery 1 in the process of charge, thereby rapidlyand appropriately charging the secondary battery 1 to its fully chargedcondition without causing excessive chemical reaction(oxidation-reduction reaction) in the secondary battery 1.

THIRD EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the thirdembodiment of the present invention will be explained.

The charging equipment of the third embodiment has such characteristicdifferent from the second embodiment that it judges whether a differenceΔe between voltage e detected by the voltage detection part 9 during thelast application of the special charging voltage E_(s) and voltage edetected by the voltage detection part 9 during the present applicationof the special charging voltage E_(s) is within a standard range W ornot. If the voltage difference Δe is not within the standard range W, itswitches applied voltage to new equilibrium voltage E_(eq) and specialcharging voltage E_(s) corresponding to another kind of secondarybattery1 and charges the secondary battery 1 with the new equilibriumvoltage E_(eq) and special charging voltage E_(s).

The charging equipment of the third embodiment is configured similarlywith that shown in FIG. 1. The storage means (memory) in the controlpart 4 stores equilibrium voltages E_(eq) and special charging voltagesE_(s) corresponding to respective kinds of secondary batteries. Thecontrol part 4 has a check current judging program and a voltagedifference judging program. The check current judging program serves asmeans for judging whether electric current i detected by the currentdetection part 3 during application of the equilibrium voltage E_(eq) islarger than a preset standard electric current J for finishing chargingor not. The voltage difference judging program serves as means forjudging whether the voltage difference Δe between voltage e detected bythe voltage detection part 9 during the last application of the specialcharging voltage E_(s) and voltage e detected by the voltage detectionpart 9 during the present application of the special charging voltageE_(s) is within the preset standard range W or not.

Explanation of other parts in the charging equipment of the thirdembodiment is omitted because they are similar with those of the firstembodiment.

The flow of charge controlling the secondary battery 1 by the chargingequipment of the third embodiment, wherein the storage means in thecontrol part 4 stores two equilibrium voltages E_(eq) (E_(eql), E_(eqh))and two special charging voltages E_(s) (E_(s1), E_(sh)) correspondingto two kinds of secondary batteries, will be explained referring to theflow chart shown in FIG. 13.

The equilibrium voltage E_(eql) is lower than the equilibrium voltageE_(eqh), and the special charging voltage E_(s1) is lower than thespecial charging voltage E_(sh).

First of all, a user manipulates the operation part 8 of the chargingequipment to start charging [step D1]. Accordingly, the chargingequipment applies the lower special charging voltage E_(s1) to thesecondary battery 1 for a determined time (a fixed time) T₁ [step D2].

The voltage detection part 9 detects voltage e applied to the secondarybattery 1 while the determined time T₁ of applying the lower specialcharging voltage E_(s1) to the secondary battery1 [step D3], and thevoltage difference judging program judges whether the voltage differenceΔe between voltage e detected by the voltage detection part 9 during thelast application of the special charging voltage E_(s) and voltage edetected by the voltage detection part 9 during the present applicationof the special charging voltage E_(s) is within the preset standardrange W or not [step D4]. If the voltage detection is the first time,the control step goes to the next step D5 without judging the voltagedifference Δe. If the voltage difference Δe is within the standard rangeW, the control step goes to the next step D5. Otherwise, the controlstep jumps to the later-mentioned step D10.

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step D5] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage to the lower equilibrium voltageE_(eql), and applies the lower equilibrium voltage E_(eq) to thesecondary battery 1 for a short time T₃ [step D6].

If the short time T₃ is set to more than 1 second, the above-mentionedstep D5 may be omitted.

The charging equipment detects electric current i flowing through thesecondary battery 1 while the short time T₃ of applying the lowerequilibrium voltage E_(eqh) to the secondary battery 1 [step D7].

Then, the check current judging program judges basing on the detectedelectric current i [step D8]. If the detected electric current i islarger than the standard electric current J for finishing charging, thecontrol step returns to the step D2, and the above steps are repeated.Otherwise, the charging equipment stops charging the secondary battery 1[step D9].

At the above mentioned step D4, if the above-mentioned voltagedifference Δe is not within the standard range W, the charging equipmentswitches applied voltage to the higher special charging voltage E_(sh),and applies the higher special charging voltage E_(sh) to the secondarybattery 1 for a determined time T₁ [step D10].

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step D11] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage to the higher equilibrium voltageE_(eqh), and applies the higher equilibrium voltage E_(eqh) to thesecondary battery 1 for a short time T₃ [step D12].

If the short time T₃ is set to more than 1 second, the above-mentionedstep D11 may be omitted.

The charging equipment detects electric current i flowing through thesecondary battery 1 while the short time T₃ of applying the higherequilibrium voltage E_(eqh) to the secondary battery 1 [step D13].

Then, the check current judging program judges basing on the detectedelectric current i [step D14]. If the detected electric current i islarger than the standard electric current J for finishing charging, thecontrol step returns to the step D10, and the above steps are repeated.Otherwise, the charging equipment stops charging the secondary battery 1[step D9].

The foregoing explanation has been given of charge control by thecharging equipment wherein the storage means in the control part 4stores two equilibrium voltages E_(eql), E_(eqh) and two specialcharging voltages E_(s1), E_(sh) corresponding to two kinds of secondarybatteries.

The control flow of charging the secondary battery 1 by the chargingequipment of the third embodiment, wherein the storage means in thecontrol part 4 stores equilibrium voltages E_(eq) (E_(eq1), E_(eq2), . .. E_(eqn)) and special charging voltages E_(s) (E_(s1), E_(s2), . . .E_(sn)) corresponding to n (n is a natural number more than 1) differentkinds of secondary batteries, will be explained referring to the flowchart shown in FIG. 14.

Voltages E_(eq1), E_(eq2), . . . E_(eqn) and voltages E_(s1), E_(s2), .. . E_(sn), are ranked from the minimum to the maximum.

First of all, a counter variable k (k=1,2, . . . ,n) is initialized to 1[step F1]. A user manipulates the operation part 8 of the chargingequipment to start charging [step F2]. Accordingly, the kth smallestspecial charging voltage E_(sk) of the n special charging voltages tothe secondary battery 1 set in the charging equipment for a determinedtime (a fixed time) T₁ [step F3].

If the k is equal to n [step F4], the control step jumps to thelater-discussed step F8. If the k is equal to or smaller than n−1, thevoltage detection part 9 detects voltage e applied to the secondarybattery 1 while the determined time T₁ of applying the kth smallestspecial charging voltage E_(sk) to the secondary battery1 [step F5]. Thevoltage difference judging program judges whether the voltage differenceΔe between the voltage e detected by the voltage detection part 9 duringthe last application of the special charging voltage E_(s) and thevoltage e detected by the voltage detection part 9 during the presentapplication of the special charging voltage E_(s) is within the presetstandard range W or not [step F6]. If the voltage difference Δe iswithin the standard range W, the control step goes to thebelow-mentioned step F8. Otherwise, the rank of k increments by 1 [stepF7], and the control step returns to the step F3. If the voltagedetection if the first time, the control step goes to the next step F8without judging the voltage difference Δe.

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step F8] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage to the kth smallest equilibriumvoltage E_(eq) k, and applies the kth smallest equilibrium voltageE_(eqk) to the secondary battery for a short time T₃ [step F9].

If the short time T₃ is set to more than 1 second, the above-mentionedstep F8 may be omitted.

The charging equipment detects electric current i flowing through thesecondary battery 1 while the short time T₃ of applying the kth smallestequilibrium voltage E_(eqk) to the secondary battery 1 [step F10].

Then, the check current judging program judges basing on the detectedelectric current i [step F11]. If the detected electric current i islarger than the standard electric current J for finishing charging, thecontrol step returns to the step F3, and the above steps are repeated.Otherwise, the charging equipment stops charging the secondary battery 1[step F12].

The foregoing charging equipment of the third embodiment has the sameeffect as the charging equipment of the first embodiment. Additionally,the charging equipment of the third embodiment identifies the kind ofsecondary battery 1 automatically in the process of charge, therebyrapidly and appropriately charging the secondary battery 1 withoutcausing excessive chemical reaction (oxidation-reduction reaction) inthe secondary battery 1 till its fully charged condition.

FOURTH EQUIPMENT FOR CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the fourthembodiment of the present invention will be explained.

The charging equipment of the fourth embodiment has such characteristicdifferent from the first embodiment that it breaks off voltage appliedto the secondary battery 1 after application of special charging voltageE_(s) for a determined time T₁, and detects the voltage differenceΔE_(s) between the special charging voltage E_(s) and open-circuitvoltage E (E_(α), E_(β), E_(γ), E_(δ)etc.) of the secondary battery 1.If the voltage difference ΔE_(s) is not larger than the standard valueK, it stops charging the secondary battery 1.

The control part 4 has a voltage difference computing program, a chargetime predicting program, and a voltage difference judging program. Thevoltage difference computing program serves as means for computing thevoltage difference ΔE_(s) between the special charging voltage E_(s) andthe open-circuit voltage E (E_(α), E_(β), E_(γ), E_(δ)etc.) of thesecondary battery 1. The charge time predicting program serves as meansfor estimating the necessary time τ to fully charge the secondarybattery 1 basing on the voltage difference ΔE_(s). The voltagedifference judging program serves as means for judging whether thevoltage difference ΔE_(s) is larger than a preset standard value K ornot. The necessary time τ computed basing on the voltage differenceΔE_(s) is indicated on the display part 7 with such as LED and LCD.

The charging equipment of the fourth embodiment comprises the displaypart 7 as an example of information means which indicates the necessarytimer to fully charge the secondary battery 1 to a user through his/hereyes. However, the charging equipment may have any other informationmeans which informs a user with sound etc. instead of the display part7.

The standard value K of the charging equipment of the fourth embodimentis a difference between the special charging voltage E_(s) and theequilibrium voltage E_(eq) which is equal to the open-circuit voltage Eof the fully charged secondary battery 1 (K=E_(s)−E_(eq)). The chargingequipment needs to be designed for controlling charge of the secondarybattery 1 so that the open-circuit voltage E_(x) should be detected inthe high impedance state where electric current does not flow throughthe target for measuring, such as the state where electric current doesnot flow through the secondary battery 1 to which the equilibriumvoltage is applied.

The necessary time τ to fully charge the secondary battery 1 will beexplained. The necessary time τ is got from the graph in FIG. 15 showingthe relation between the voltage difference ΔE_(s) and the necessarytime τ to fully charge the secondary battery 1. Referring to FIG. 3,when the secondary battery 1 whose charging rate is approximately 0% ischarged, the open-circuit voltage E of is equal to is equal to E_(α),the voltage difference ΔE_(s) is therefore a difference between thevoltages E_(s) and E_(α) (ΔE_(s)=E_(s)−E_(α)), and the necessary time τto fully charge is now assumed to be a time τ_(α). It is understood fromthe graph of FIG. 3 that the necessary time τ and the voltage differenceΔE_(s) are reduced according to the passage of charge of the secondarybattery 1. The necessary time τ to fully charge the secondary battery 1becomes 0 when the voltage difference ΔE_(s) reaches the preset standardvalue K (in this case, the standard value K is equal to the differencebetween the voltages E_(s) and E_(eq) (K=E_(s)−E_(eq))), or in otherwords, when the secondary battery 1 is fully charged (its charging ratereaches 100%). Therefore, if the charge time predicting program has thisgraph, or a relational expression which formulates the relation betweenthe voltage difference ΔE_(s) and the necessary timer led from thegraph, the necessary timer to fully charge the secondary battery 1 canbe estimated basing on the voltage difference ΔE_(s).

Explanation of other parts in the charging equipment of the fourthembodiment is omitted because they are similar with those of the firstembodiment.

The control flow of charging the secondary battery 1 by the chargingequipment of the fourth embodiment will be explained referring to theflow chart shown in FIG. 16.

First of all, a user inputs data about a kind of secondary battery 1 tobe charged to the control part 4 by manipulating the operation part 8,so as to select special charging voltage E_(s) and equilibrium voltageE_(eq) in correspondence to the kind of secondary battery 1 from a tableof the storage means in the control part 4 [step G1].

The user manipulates the operation part 8 to start charging [step G2].Accordingly, the charging equipment applies the corresponding specialcharging voltage E_(s) to the secondary battery 1 for a determined time(a fixed time) T₁ [step G3]. The determined time T₁ is calculated basingon variation of charging electric current according to the time progressduring the application of the special charging voltage E_(s).

After the determined time T₁ passes, the charging equipment breaks offapplication of the special charging voltage E_(s) for a time T₄ [stepG4]. In the meanwhile, the voltage detection part 9 detects open-circuitvoltage E E_(α), E_(β), E_(γ), E_(δ), etc.) of the secondary battery 1[step G5], and the voltage difference ΔE_(s) between the specialcharging voltage E_(s) and the open-circuit voltage E_(x) is computed[step G6].

Then, the voltage difference judging program judges basing on thiscomputed voltage difference ΔE_(s) [step G7]. If the computed voltagedifference ΔE_(s) is larger than the standard value K, the control stepreturns to the step G3, and the above steps are repeated. Otherwise, thecharging equipment assumes that the secondary battery 1 is fullycharged, and it stops charging the secondary battery 1 [step G8].

Incidentally, the necessary time τ to fully charge the secondary battery1 can be calculated basing on the computed value of voltage differenceΔE_(s), though it is not written in the flow chart of FIG. 16. Thischarging equipment indicates the necessary timer to fully charge thesecondary battery 1 on the display part 7 for users' convenience. Thecharging time T₁ when applying the special charging voltage E_(s) variesaccording to the battery's capacity, structure, form, or the like. Ifthe secondary battery 1 is an AA size nickel-cadmium battery or an AAsize nickel-hydrogen battery, for example, the charging time T₁ is setto a time between 60 seconds and 90 seconds. The break-off time T₄ isdetermined as a time required for the voltage applied between theterminals of the secondary battery 1 to become so stable as to bemeasured. If the above-mentioned battery serves as the secondary battery1 to be charged, the break-off time T₄ is set to a time between 1 secondand 5 seconds. The charging equipment of the fourth embodimentcontrolling the voltage applied to the secondary battery 1 andperiodically checking the charged condition of the secondary battery 1by the above method can appropriately charge the secondary battery 1without causing excessive damaging chemical reaction(oxidation-reduction reaction) therein, thereby increasing effectivebattery cycles of the secondary battery 1. Also, the charging equipmentusing the above method can accurately judge whether the secondarybattery 1 is fully charged or not, because it detects the voltagedifference between the special charging voltage E_(s) and theopen-circuit voltage E_(x) of the secondary battery 1. Additionally, thecharging equipment can remarkably reduce the charging time because itsupplies the secondary battery 1 with pretty large charging current bymainly applying the special charging voltage E_(s) larger than theequilibrium voltage E_(eq).

FIFTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the fifthembodiment of the present invention will be explained.

The charging equipment of the fifth embodiment has such characteristicdifferent from the first embodiment that its control part 4 has avoltage difference judging program for comparing a difference ΔE_(eq)between the equilibrium voltage E_(eq) and open-circuit voltage E(E_(α), E_(β), E_(γ), E_(δ), etc.) of the secondary battery 1 withstandard voltage of 0V, so that, if the volt difference ΔE_(eq) islarger than 0V, the special charging voltage E_(s) is applied to thesecondary battery 1 and the charge control are repeated; otherwise, itis assumed that the secondary battery 1 is fully charged, therebyhalting charge control of the secondary battery1.

Explanation of other parts in the charging equipment of the fifthembodiment is omitted because they are similar with those of the fourthembodiment.

The control flow of charging the secondary battery 1 by the chargingequipment of the fifth embodiment will be explained referring to theflow chart shown in FIG. 17.

First of all, a user inputs data of a kind of secondary battery 1 to becharged to the control part 4 by manipulating the operation part 8, soas to select special charging voltage E_(s) and equilibrium voltageE_(eq) in correspondence to the kind of secondary battery 1 from a tableof the storage means in the arithmetic and control part 4 [step H1].

The user manipulates the operation part 8 to start charging [step H2].Accordingly, the charging equipment applies the corresponding specialcharging voltage E_(s) to the secondary battery 1 for a determined time(a fixed time) T₁ [step H3].

After the determined time T₁ passes, the charging equipment breaks offapplication of the special charging voltage E_(s) for a time T₄ [stepH4]. In the meanwhile, the voltage detection part 9 detects open-circuitvoltage E E_(α), E_(β), E_(γ), E_(δ), etc.) of the secondary battery 1[step H5].

The control flow from the step H1 to the step H5 according to the fifthembodiment is similar with that from the step G1 to the step G5according to the fourth embodiment. Next, the voltage differencecomputing program computes the voltage difference ΔE_(eq) between theequilibrium voltage E_(eq) and the open-circuit voltage E of thesecondary battery 1 [step H6].

Then, the voltage difference judging program judges basing on thiscomputed voltage difference ΔE_(eq) [step H7]. When the computed voltagedifference ΔE_(eq) is larger than the standard value of 0V, the controlstep returns to the step H3, and the above steps are repeated.Otherwise, the charging equipment recognizes that the secondary battery1 is fully charged, and it stops charging the secondary battery 1 [stepH8].

By the charging equipment of the fifth embodiment using theabove-mentioned method, any kind of secondary battery 1 can be easilyand accurately assumed to be fully charged when the voltage differenceΔE_(eq) is not larger than 0V.

Instead of computing the voltage difference ΔE_(eq) between theequilibrium voltage E_(eq) and the open-circuit voltage E of thesecondary battery 1, the charging equipment may alternatively comparethe open-circuit voltage E with the equilibrium voltage E_(eq). If theopen-circuit voltage E is smaller than the equilibrium voltage E_(eq),the special charging voltage E_(s) higher than the equilibrium voltageE_(eq) is applied to the secondary battery 1 and the charge controlsteps are repeated; otherwise, charging the secondary battery 1 ishalted.

SIXTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the sixthembodiment of the present invention will be explained.

The charging equipment of the sixth embodiment has such a characteristicdifferent from the first embodiment that it stops charging the secondarybattery 1 after the necessary time t computed basing on the detectedcheck electric current i passes.

The charging equipment of the sixth embodiment is configured similarlywith that of FIG. 1. Its control part 4 has a charge time predictingprogram and an observation program. The charge time predicting programserves as means for estimating the necessary time t to fully charge thesecondary battery 1 basing on the detected electric current i duringapplication of the equilibrium voltage E_(eq) to the secondary battery1. The observing program serves as means for observing the passage ofnecessary time t from the moment when the necessary time t is computed.

The control flow of charging the secondary battery 1 by the chargingequipment of the sixth embodiment will be explained referring to theflow chart shown in FIG. 18.

First of all, a user inputs data of a kind of secondary battery 1 to becharged to the control part 4 by manipulating the operation part 8, soas to select special charging voltage E_(s) and equilibrium voltageE_(eq) in correspondence to the kind of secondary battery 1 from a tableof the storage means in the control part 4 [step M1].

The user manipulates the operation part 8 to start charging [step M2].Accordingly, the charging equipment applies the corresponding specialcharging voltage E_(s) to the secondary battery 1 for a determined time(a fixed time) T₁ [step M3].

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step M4] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage to the equilibrium voltage E_(eq),and applies the equilibrium voltage E_(eq) to the secondary battery 1for a short time T₃ [step M5].

If the short time T₃ is set to more than 1 second, the above-mentionedstep M4 may be omitted.

The charging equipment detects a value of electric current i flowingthrough the secondary battery 1 while the short time T₃ of applying theequilibrium voltage E_(eq) to the secondary battery 1 [step M6]. Next,the charge time predicting program calculates the necessary time t tofully charge the secondary battery 1 basing on the detected value ofelectric current i, that is, the time t required for the detectedelectric current i to reach the standard electric current J forfinishing charging (that is a value of electric current detected at thefully charged condition), and the necessary time t is indicated on thedisplay part 7 [step M7].

This control flow from the step M1 to the step M7 according to the sixthembodiment is the same with that from the step A1 to the step A7according to the first embodiment. Next, the observation program judgeswhether the necessary time t to fully charge is more than 0 second ornot [step M8]. If the necessary time t to fully charge is more than 0second, the control step goes to the step M9 so as to apply the specialcharging voltage E_(s) to the secondary battery 1 for a time T₅ [stepM8]. After the time T₅ passes, the control step returns to the step M8,and the observation program judges whether the necessary time t to fullycharge has passed or not. At the step M8, if the necessary time t tofully charge is not more than 0 second, in other words, if the necessarytime t to fully charge has passed, the charging equipment decides thatthe secondary battery 1 is fully charged, and it stops charging thesecondary battery 1 automatically [step M10].

Explanation of other parts in the charging equipment of the sixthembodiment is omitted because they are similar with those of the firstembodiment.

In the flow chart for controlling the charging equipment shown in FIG.9, once the necessary time t to fully charge is calculated basing on thedetected electric current i, the charging equipment continuesapplication of the special charging voltage E_(s) to the secondarybattery 1, and after the necessary time t has passed, the chargingequipment stops charging the secondary battery 1 automatically.Alternatively, at the above-mentioned step M8, if the necessary time tis more than 0 second, the control step may return to the step M3, andthe above-mentioned charge control steps may be repeated; otherwise thecharging equipment stops charging the secondary battery 1.

As mentioned above, the charging equipment automatically stoppingcharging a secondary battery after the necessary time t passes can beconfigured simply and surely stop charge of the secondary battery.According to this charging equipment, the secondary battery 1 can becharged appropriately without causing excessive damaging chemicalreaction (oxidation-reduction reaction) therein till its fully chargedcondition, thereby increasing its effective battery cycles.Additionally, it is more convenient for a user to monitor the necessarytime t to fully charge the secondary battery 1.

SEVENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the seventhembodiment of the present invention.

The charging equipment of the seventh embodiment has such characteristicdifferent from the first embodiment that it stops charging the secondarybattery 1 after the charging rate ρ computed basing on the detectedcheck electric current i reaches a standard value.

The charging equipment of the seventh embodiment is configured similarlywith that of FIG. 1. Its control part 4 has a charging rate computingprogram and a charging rate judging program. The charging rate computingprogram serves as means for computing the charging rate ρ of thesecondary battery 1 at the moment when the current detection part 3detects electric current i while applying the equilibrium voltage E_(eq)to the secondary battery 1. The charging rate judging program serves asmeans for judging whether the charging rate ρ computed by the chargingrate computing program is larger than a preset standard value L or not.

The above-mentioned FIG. 4 is a graph showing the necessary time t tofully charge a secondary battery 1 relative to detected electric currenti in the secondary battery 1 while the equilibrium voltage E_(eq) isapplied to the secondary battery 1. Either a conversion table forconverting the check current i into the charging rateρor a relationalexpression formulating the relation between the check current i and thecharging rateρis formed basing on the graph of FIG. 4 about a secondarybattery 1 to be charged and it is provided for the charging ratecomputing program, thereby facilitating for easy computing the chargingrateρ of the secondary battery 1.

The control flow of charging the secondary battery 1 by the chargingequipment of the seventh embodiment will be explained referring to theflow chart shown in FIG. 19.

First of all, a user inputs data of a kind of secondary battery 1 to becharged to the control part 4 by manipulating the operation part 8, soas to select special charging voltage E_(s) and equilibrium voltageE_(eq) in correspondence to the kind of secondary battery 1 from a tableof the storage means in the control part 4 [step N1].

The user manipulates the operation part 8 to start charging [step N2].Accordingly, the charging equipment applies the corresponding specialcharging voltage E_(s) to the secondary battery 1 for a determined timeT₁ [step N3].

After the determined time T₁ passes, the charging equipmentshort-circuits the secondary battery 1 between its terminals for anextremely short time T₂ [step N4] so as to remove electric charge fromthe electrode interface of the secondary battery 1. Then, the chargingequipment switches applied voltage to the equilibrium voltage E_(eq),and applies the equilibrium voltage E_(eq) to the secondary battery 1for a short time T₃ [step N5].

If the short time T₃ is set to more than 1 second, the above-mentionedstep N4 may be omitted.

The charging equipment detects electric current i flowing through thesecondary battery 1 while the short time T₃ of applying the equilibriumvoltage E_(eq) to the secondary battery 1 [step N6]. This control flowfrom the step Ni to the step N6 according to the sixth embodiment is thesame with that from the step A1 to the step A6 according to the firstembodiment. The charging rate computing program computes the chargingrate ρ of the secondary battery 1 basing on the detected electriccurrent i, and the computed charging rate ρ is indicated on the displaypart 7 [step N7].

Then, the charging rate judging program judges basing on the computedcharging rate ρ [step N8]. If the charging rate ρ is lower than astandard value L (for example, L=95%), the control step returns to thestep N3, and the above steps are repeated. Otherwise, the chargingequipment stops charging the secondary battery 1 [step N9].

Explanation of other parts in the charging equipment of the seventhembodiment is omitted because they are similar with those of the firstembodiment.

By stopping charging the secondary battery 1 automatically when thecharging rate ρ is not lower than the standard value L, the chargingequipment can be configured simply for appropriate charge of thesecondary battery 1 without causing excessive damaging chemical reaction(oxidation-reduction reaction) therein till its fully charged conditionsuch as to greatly increase effective battery cycles of the secondarybattery 1.

Furthermore, it is more convenient for a user to monitor the chargingrate ρ of the secondary battery 1.

EIGHTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the eighthembodiment of the present invention will be explained.

The charging equipment of the eighth embodiment is so configured asshown in FIG. 20. A reference numeral 1 designates a secondary battery,and a reference numeral 12 designates a power supply part. The powersupply part 2 includes a transformer-rectifier circuit for changingcommercial alternating current into direct current. A reference numeral13 designates a mass capacitor (an electrolysis capacitor, electricdouble layer capacitor, or the like). Both of the capacitor 13 and thesecondary battery 1 are connected in parallel to the power supply part12. A switch 17 is interposed between the power supply part 12 and thecapacitor 13, and a switch 18 is interposed between the capacitor 13 andthe secondary battery 1. A reference numeral 14 designates a currentdetection part from detecting charting electric current flowing to thesecondary battery 1. The electric current i detected by the currentdetection part 14 is transmitted to a control part 15. The control part15 selectively opens or shuts the switch 17 and the switch 18, andjudges whether the secondary battery 1 is fully charged or not. That isto say, the control part 15 has a current judging program serving asmeans for judging whether the electric current i detected by the currentdetection part 14 is larger than a preset standard electric current Jfor finishing charging or not. A reference numeral 16 designates a checkpower supply part for applying check voltage to the secondary battery 1basing on the command from the control part 15.

The method for charging the secondary battery 1 by the chargingequipment of the eighth embodiment is as follows: The capacitor 13stores up electricity by applying determined power-supply voltage to thecapacitor 13 for a determined time T₆, with the switch 17 closed and theswitch 18 open. After the determined time T₆ passes, electric chargestored in the capacitor 13 is transmitted to the secondary battery 1 byopening the switch 17 and shutting the switch 18. Repeating thesecontrol steps, the secondary battery 1 is charged. In this chargingflow, the method for judging whether the secondary battery 1 is fullycharged or not is as follows: While the capacitor 13 is separated fromthe secondary battery 1 and stores electric charge, the check powersupply part 16 applies check voltage E_(c) to the secondary battery 1,the current detection part detects electric current i flowing to thesecondary battery 1, and the control part 15 judges basing on thedetected value of electric current i whether the secondary battery 1 isfully charged.

The control flow of charging the secondary battery 1 by the chargingequipment of the eighth embodiment will be explained referring to theflow chart shown in FIG. 21.

First of all, a user manipulates the operation part (not shown) to startcharging [step P1]. Accordingly, the control part 15 transmits commandto both the switch 17 and the switch 18 on the circuit shown in FIG. 20such as to shut the switch 17 and open the switch 18 [step P2].

The power supply part 15 applies predetermined power-supply voltage,e.g. voltage higher than the equilibrium voltage E_(eq) to the capacitor13 having large capacity for a determined time T₆ [step P3], whereby thecapacitor 13 stores up electricity.

While the capacitor 13 stores electric charge, the check power supplypart 16 applies the check voltage to the secondary battery 1 separatedfrom the capacitor 13 [step P4]. In the case of charging by the chargingequipment of the eighth embodiment, the check voltage is the equilibriumvoltage E_(eq). At this time, the current detection part 14 detectselectric current i flowing to the secondary battery 1 [step P5].

Next, the current judging program compares the detected electric currenti with the standard electric current J for finishing charging [step P6].If the detected electric current i is larger than the standard electriccurrent J for finishing charging, the control step goes to the step P7,and the control part 15 transmits a command to both the switch 17 andthe switch 18 on the circuit such as to open the switch 17 and close theswitch 18, thereby transmitting electricity stored in the capacitor 13to the secondary battery 1 [step P8]. After a time T₇ passes, thecontrol step returns to the step P2 so that the switch 17 is closed andthe switch 18 is opened, and the above steps including storing andcharging electricity are repeated. If the detected electric current i isnot larger than the standard electric current J for finishing chargingat the above-mentioned step P6, the charging equipment assumes that thesecondary battery 1 is fully charged, and it stops charging thesecondary battery 1 [step P9].

The equilibrium voltage E_(eq) is suitable for serving as the checkvoltage for easily judging whether the secondary battery 1 is fullycharged or not, because the electric current becomes almost 0 mA whenits charging rate reaches 100% (the fully charged condition), asunderstood from the graph showing in FIG. 3. However, even if thesecondary batteries 1 are identical in classification, the equilibriumvoltage E_(eq) of each secondary battery 1 is slightly different fromone another. To prevent overcharging in consideration of such situation,the standard voltage J for finishing charging is desirably set to beabout 10 mA, for example, considerably higher than 0 mA.

The charging equipment of the eighth embodiment using such a chargingmethod as to transmit electricity stored in the capacitor 13 to thesecondary battery 1 facilitates for measuring the amount of electricitycharged into the secondary battery 1. Furthermore, the chargingequipment using the capacitor 13 having large capacity can charge highelectricity, i.e., high electric current to the secondary battery 1 fora short time, thereby reducing the time required for charging.Furthermore, the charging equipment can monitor the charged condition ofthe secondary battery 1 by periodically detecting the electric current iflowing through the secondary battery 1 while applying the equilibriumvoltage (check voltage) E_(eq) to the secondary battery 1 periodically,so that it can charge the secondary battery 1 appropriately till thefully charged condition so as to prevent such overcharging as to causeexcessive damaging chemical reaction (oxidation-reduction reaction),thereby increasing effective battery cycles of the secondary battery 1.Also, the check voltage is applied to the secondary battery not from theelectric power supply part 12 but from the check electric power supplypart 16 so as to enable monitoring the charged condition of thesecondary battery during the electricity storing process of thecapacitor 13, thereby further reducing the charging time. Furthermore,the charging equipment according to the eighth embodiment isadvantageously reliable in its simple structure and its easy chargingmethod.

The foregoing explanation of this charging equipment for a secondarybattery 1 of the eighth embodiment is only a concrete example. It may bemodified without departing from the scope of appended claims. Forexample, in the above statement, electric current i is detected whileapplying the equilibrium voltage E_(eq) to the secondary battery 1,however, another voltage may be alternatively applied for detectingelectric current i. The check electric power supply part 16 separatedfrom the electric power supply part 12 facilitates for checking thecharged condition of the secondary battery 1 while theelectricity-storing duration of the capacitor 13. However, voltagecontrolled by the electric power supply part 12 may be alternativelyapplied to the secondary battery 1 for checking the charged conditionthereof.

NINTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to the ninthembodiment of the present invention will be explained.

The charging equipment of the ninth embodiment is configuredsubstantially similarly with that of the eighth embodiment, however, itis different from that the eighth embodiment in that it has no checkpower supply part 16 and has a check voltage detection part 14 replacingthe check current detection part 16 shown in FIG. 20 so as to judgewhether the secondary battery 1 is fully charged basing on the detectedvoltage of the secondary battery 1. This charging equipment of the ninthembodiment is provided with a control part 15 having a voltage judgingprogram serving as means for judging whether the open-circuit voltage E(E_(α), E_(β), E_(γ), E_(δ), etc.) of the secondary battery 1 is largerthan its equilibrium voltage E_(eq).

To explain the method for judging concretely, the charging equipmentdetects the open-circuit voltage E (E_(α), E_(β), E_(γ), E_(δ), etc.) ofthe secondary battery 1 while the capacitor 13 stores up electricity,that is, while the connection between the capacitor 13 and the secondarybattery 1 is broken. If the detected open-circuit voltage E is smallerthan the equilibrium voltage E_(eq), the charging equipment keeps upcharging process. Otherwise, the charging equipment stops charging.

The control flow of charging the secondary battery 1 by the chargingequipment of the ninth embodiment will be explained referring to theflow chart shown in FIG. 22.

First of all, a user manipulates the operation part (not shown) to startcharging [step Q1]. Accordingly, the control part 15 transmits commandto both the switch 17 and the switch 18 on the circuit shown in FIG. 20such as to shut the switch 17 and open the switch 18 [step Q2].

The power supply part 15 applies predetermined power-supply voltage,e.g. voltage higher than the equilibrium voltage E_(eq) to the capacitor13 having large capacity for a determined time T₆, thereby storingelectricity in the capacitor 13 [step Q3].

While the capacitor 13 stores electricity, that is, while the connectionbetween the capacitor 13 and the secondary battery 1 is broken, thevoltage detection part detects the open-circuit voltage E_(x) of thesecondary battery 1 [step Q4]. Next, the voltage judging programcompares the detected open-circuit voltage E_(x) with the equilibriumvoltage E_(eq) [step Q5]. If the detected open-circuit voltage E_(x) issmaller than the equilibrium voltage E_(eq), the control step goes tothe step Q6, and the control part 15 transmits command to both theswitch 17 and the switch 18 on the circuit such as to open the switch 17and close the switch 18. Then, electricity stored in the capacitor 13 istransmitted into the secondary battery 1 [step Q7]. After a time T₇passes, the control step returns to the step Q2 so that the switch 17 isclosed and the switch 18 is opened, and the above steps includingstoring and charging electricity are repeated. On the other hand, if thedetected open-circuit voltage E_(x) is not smaller than the equilibriumvoltage E_(eq), the charging equipment assumes that the secondarybattery 1 is fully charged, and stops charging the secondary battery 1[step Q8]. Explanation of other structure and effect of the chargingequipment of the ninth embodiment is omitted because they are almostsimilar to those of the charging equipment of the eighth embodiment.

Next, the amount of electricity charged to the secondary battery 1 andthe necessary time to fully charge the secondary battery 1 every storingelectricity in the capacitor 13 are theoretically calculated accordingto the transient-phenomenon theory, basing on each of equivalentcircuits shown in FIGS. 23( a), 23(b) and 23(c), each of which serves asa basic circuit for charging the secondary battery 1 by either thecharging equipment of the eighth embodiment or ninth embodiment. FIG.23( a) is an equivalent circuit diagram serving as a basic circuit forcharging the secondary battery 1 to the block diagram in FIG. 20. FIG.23( b) is an equivalent circuit diagram for storing electricity in thecapacitor 13 for a time T₆ with the switch 17 shut and the switch 18opened. FIG. 23( c) is an equivalent circuit diagram for transmittingelectricity stored in the capacitor 13 to the secondary battery 1 for atime T₇ with the switch 17 opened and the switch 18 shut. In FIG. 23, Eis power-supply voltage, r is internal resistance of power supply part12, C is electrostatic capacity of the capacitor 13, and R is internalresistance of the secondary battery 1. If V designates initial voltagecaused by residual electricity in the capacitor 13, and Q₁ designatesthe amount of electricity charged to the secondary battery 1 at thefirst time, Q₁ is expressed with the following formula (1).Q ₁ =C*(E−V)e ^(−T1/rC)*(1−e ^(−T2/RC))  (1)

Q₂, designating the amount of electricity charged to the secondarybattery 1 at the second time, is expressed with the following formula(2).Q ₂ =C*{E−(E−V)e ^(−T1/rC) *e ^(−T2/RC) }*e ^(−T1/rC)*(1−e^(−T2/RC))  (2)

Additionally, Q₃, designating the amount of electricity charged to thesecondary battery 1 at the third time, is expressed with the followingformula (3).Q ₃ =C*[E−{E−(E−V)e ^(−T1/rC) *e ^(−T2/RC) }*e ^(−T1/rC) *e ^(−T2/RC)]*e ^(−T1/rC)*(1−e ^(−T2/RC))  (3)

Q_(n), designating the amount of electricity charged to the secondarybattery 1 at the nth time, is expressed with the following formula (4)generalized from the formulas (1), (2) and (3).Q _(n) =C*[E*{1−e ^(−(a+b)) +e ^(−2(a+b)) −e ^(−3(a+b)) . . .+(−1)^((n−1)) *e _(−(n−1)(a+b))+(−1)^(n) *V*e ^(31 (n−1)(a+b)) }*e^(−a)*(1−e ^(−b))  (4)

In the formula (4), it is defined that a=T1/rC, and b=T2/RC. It isassumed that r (internal resistance of the power supply part 12) is1Ω(ohm), R (internal resistance of the secondary battery 1) is 1 Ω, C(electrostatic capacity of the capacitor 13) is 1 F(farad), V (initialvoltage of the capacitor 13) is 0V, the time T1 is 1 second, and thetime T2 is 1 second. Each electricity Q₁, Q₂, Q₃ is calculated so thatQ₁=11.63 C(coulomb), Q₂=10.00 C, and Q₃=10.26 C. If electricity chargedto the secondary battery 1 per 2 seconds is assumed to sums up to about10.00 C basing on the calculated values, the necessary time to fullycharge the secondary battery whose charge capacity is 1600 mAh iscalculated to be about 5 minutes.

TENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERIES

A charging equipment for a plurality of secondary batteries 1 accordingto the tenth embodiment of the present invention will be explained.

The charging equipment according to the tenth embodiment shown as ablock diagram in FIG. 24 is provided for a plurality of secondarybatteries 1.

In FIG. 24, a reference numeral 20 designates a battery box in which aplurality of secondary batteries 1 are aligned. A reference numeral 22designates a power supply part including a transformer-rectifier circuitfor changing commercial alternating current into direct current. Areference numeral 23 designates a charging voltage control part forcontrolling charging voltage applied to the secondary battery 1. Areference numeral 24 designates a check voltage control part forcontrolling check voltage applied to the secondary battery 1 to checkthe charged condition of the secondary battery 1. A reference numeral 25designates a current detection part for detecting electric currentflowing through the secondary battery 1 during the application of checkvoltage. The electric current i detected by the current detection part25 is transmitted to a control part 26. The control part 26 judgeswhether the secondary battery 1 is fully charged or not, transmitscommand for applying voltage to the secondary battery 1 and command forswitching the secondary battery l to be charged, counts the number ofthe secondary batteries 1 that have been charged, and calculates thenecessary time t to fully charge the secondary battery 1. That is tosay, the control part 26 has a check current judging program, a chargetime predicting program, a count program, and the like. The checkcurrent judging program serves as means for judging whether the checkcurrent i detected by the current detection part 25 during applicationof the equilibrium voltage E_(eq) to the secondary battery 1 is largerthan preset standard electric current J for finishing charging. Thecharge time predicting program serves as means for estimating thenecessary time t to fully charge the secondary battery 1 basing on thecheck current i detected by the current detection part 25 duringapplication of the equilibrium voltage E_(eq) to the secondary battery1. The count program serves as means for counting the number of thefully charged secondary batteries 1.

A reference numeral 27 designates a voltage switching part for switchingapplied voltage between charging voltage and check voltage basing oncommand from the control part 26. A reference numeral 28 designates abattery switching part for switching a target connected to the circuitincluding the charging voltage control part 23, the check voltagecontrol part 24, and the like from the just fully charged secondarybattery 1 to the next uncharged secondary battery 1. Moreover, areference numeral 29 designates a display part for displaying thenecessary time t to fully charge the secondary battery 1 calculated inthe control part 26, or the charged condition of the presently chargedsecondary battery 1 for deciding whether charge of the secondary battery1 is finished or not.

The charging equipment of the tenth embodiment comprises the displaypart 29 as an example of information means for indicating the necessarytime t to fully charge the secondary battery 1 etc. to a user throughhis/her eyes, however, the information means may alternatively informwith sound or any other means.

The charging equipment of the tenth embodiment charges a plurality ofsecondary batteries 1 one by one. This charging equipment, taking theabove-mentioned characteristic in charging the secondary battery 1 intoconsideration, uses the following control for charging the secondarybattery 1 rapidly without damaging the secondary battery 1.

In detail, the charging equipment of the tenth embodiment applies thespecial charging voltage E_(s) to the first secondary battery 1 of the Nsecondary batteries 1 aligned in parallel for a determined time T₁ so asto charge the first secondary battery 1. After charging with highelectric current by applying the special charging voltage E_(s), thecharging equipment switches voltage applied to the first secondarybattery 1 from the special charging voltage E_(s) to the check voltageE_(c), and applies the check voltage E_(c) to the first secondarybattery 1 for a short time T₃. The above-mentioned equilibrium voltageE_(eq) may preferably serve as the check voltage E_(c).

Then, the charging equipment detects electric current i flowing throughthe first secondary battery 1 during the application of the checkvoltage _(c) to the first secondary battery 1, and compares the electriccurrent i with preset standard electric current J for finishing charging(electric current assumed to be detected when the secondary battery 1 isfully charged). If the detected electric current i is larger than thestandard electric current J for finishing charging, the chargingequipment charges the first secondary battery 1 again by applying thespecial charging voltage E_(s). Otherwise, the charging equipmentassumes that the first secondary battery 1 is fully charged, and stopscharging the first secondary battery 1. At this time, the batteryswitching part 28 serving as the battery switching means receives asignal for finishing charging from the control part 26, and switches thetarget secondary battery 1, to which the circuit is connected, from thefirst secondary battery 1 to the next uncharged secondary battery 1, andthe charging equipment charges the next uncharged secondary battery 1according to the charge control similar with that for the first chargedsecondary battery 1. In this way, the charging equipment repeats thischarge control till all of the N secondary batteries 1 are fullycharged.

Moreover, basing on the detected electric current i, the chargingequipment of the tenth embodiment judges whether the secondary battery 1is fully charged or not, and calculates the necessary time t to fullycharge the secondary battery 1. The charging equipment indicates theresult of the judgment and the necessary time t on the display part 29(monitoring means) with LED, LCD, or the like.

The control flow of charging the secondary battery 1 by the chargingequipment of the tenth embodiment will be explained referring to theflow chart shown in FIG. 25.

To give an example of charging, the charging equipment of the tenthembodiment charges N secondary batteries 1.

First of all, a counter variable m (m=0, 1, 2, . . . N) designating thenumber of the charged secondary batteries 1 is initialized to 0 [stepR1].

Next, m+1 is substituted for the counter variable m [step R2], and thecontrol step goes to the next step R3. At the step R3, a usermanipulates the operation part (not shown) of the charging equipment tostart charging. Accordingly, the special charging voltage E_(s) higherthan the equilibrium voltage E_(eq) is applied to the secondary battery1 set in the charging equipment for a determined time T₁ [step R4]. Thedetermined time T₁ is calculated basing on variation of chargingelectric current according to the time progress during application ofthe special charging voltage E_(s).

After the determined time T₁ passes, the charging equipment switchesapplied voltage from the special charging voltage E_(s) to the checkvoltage E_(c), e.g., the equilibrium voltage E_(eq) [step R5]. Then, thecurrent detection part 25 detects electric current i flowing through thesecondary battery 1 during application of the check voltage E_(c) to thesecondary battery 1 for a short time T₃ [step R6].

The check current judging program compares the detected electric currenti with the standard electric current J for finishing charging (theelectric current assumed to be detected when charging is finished) [stepR7]. If the detected electric current i is larger than the standardelectric current J for finishing charging, the control step returns tothe step R4, and the charging equipment applies the special chargingvoltage E_(s) to the secondary battery 1, and the above-mentioned chargecontrol steps are repeated. Otherwise, the charging equipment assumesthat the secondary battery 1 is fully charged, and the control step goesto the next step R8. At the step R8, the count program judges whetherthe turn of the presently charged secondary battery 1 is the final Nthor not. If the turn of the presently charged secondary battery 1 doesnot reach the Nth, the control step goes to the step R9, and the batteryswitching part 28 switches the connection of the circuit from thepresently charged secondary battery 1 to the next uncharged secondarybattery 1, and the control steps returns to the step R2, and theabove-mentioned control steps are repeated.

On the other hand, if the turn of the presently charged secondarybattery is the final Nth, the charging equipment assumes that all of thesecondary batteries 1 are fully charged, and it stops charging [stepR10].

Incidentally, the charging time T₁ for applying the special chargingvoltage E_(s) to each secondary battery 1 varies according to thecapacity, structure, form, or another element of the battery 1. Forexample, with respect to the nickel-cadmium battery, the charging timeT₁ for applying the special charging voltage E_(s) is set to about 120seconds, and the short time T₃ for applying the check voltage E_(c) isset to around 0.1 second. As mentioned above, the equilibrium voltageE_(eq) serving as the check voltage E_(c) is ideal for judging whetherthe secondary battery 1 is fully charged or not, because, when thecharging rate of the secondary battery 1 receiving the equilibriumvoltage E_(eq) reaches 100% (when the secondary battery 1 is fullycharged), the detected electric current i flowing through the secondarybattery 1 becomes almost 0 mA. However, when applying the equilibriumvoltage E_(eq) serving as the check voltage E_(c), the detected electriccurrent of different secondary batteries 1 slightly differ even if thesecondary batteries 1 are of the same type. Therefore, to prevent thesecondary battery 1 from overcharging, the standard electric current Jfor finishing charging is desirably set to considerably more than 0 mA,e.g. about 10 mA.

The charging equipment of the tenth embodiment automatically switches atarget to which its charging circuit is connected from the just fullycharged secondary battery 1 to the next uncharged secondary battery 1.By such easy charge-controlling manner, the charging equipment of thetenth embodiment surely charges all the secondary batteries 1.

Additionally, when charging each secondary battery 1, the chargingequipment periodically applies the check voltage E_(c) to the secondarybattery 1 and detects the electric current i during the application ofthe check voltage so as to judge whether the secondary battery 1 isfully charged or not, thereby preventing the secondary batteries frombeing uncharged or overcharged causing excessive chemical reaction(oxidation-reduction reaction) therein. Accordingly, all of thesecondary batteries 1 are charged appropriately till each of them isfully charged, and are prevented from being damaged therein, therebyincreasing their effective battery cycles.

Moreover, by this manner, the special charging voltage E_(s) higher thanthe equilibrium voltage E_(eq) is mainly applied to the secondarybattery 1 so as to charge each of the secondary batteries 1, so thatconsiderably high electric current flows to each secondary battery 1.Therefore, even if a plurality of secondary batteries 1 are charged oneby one, the charging equipment the time required to fully charge eachsecondary battery 1 is reduced so as to reduce the total time requiredto fully charge all the secondary batteries 1.

Furthermore, the display part 29 indicates the charged condition of thesecondary battery 1 about whether it is fully charged or not, or thenecessary time t to fully charge it, thereby being convenient for a userto monitor the present charged condition of the secondary battery or thetime required for fully charging the secondary battery.

ELEVENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERIES

A charging equipment for a plurality of secondary batteries 1 accordingto the eleventh embodiment of the present invention will be explained.

The charging equipment of the eleventh embodiment has such differentpoints from that of the tenth embodiment as follows: In the chargingequipment of the eleventh embodiment, instead of the check voltagecontrol part 24, the voltage switching part 27 for switching appliedvoltage between the charging voltage and the check voltage also switcheson and off application of voltage; and a voltage detection part replacesthe current detection part 25. The voltage detection part measures theopen-circuit voltage E (E_(α), E_(β), E_(γ), E_(δ), etc.) of thesecondary battery 1 while charging voltage is stopped being applied tothe secondary battery 1 by the voltage switching part 27.

In detail, the charging equipment of the eleventh embodiment charges thefirst secondary battery 1 of aligned N secondary batteries 1 with highelectric current by applying the special charging voltage E_(s) to thesecondary battery 1 for a determined time T₁, and then, it breaks offapplication of the special charging voltage E_(s) and detectsopen-circuit voltage E (E_(α), E_(β), E_(γ), E_(δ), etc.) of the firstsecondary battery 1 and computes the voltage difference ΔE_(s) betweenthe special charging voltage E_(s) and the open-circuit voltage E_(x).Then, the charging equipment compares this computed voltage differenceΔE_(s) with a preset standard value K. If the voltage difference ΔE_(s)is larger than the standard value K, the charging equipment furtherapplies the special charging voltage E_(s) to the first secondarybattery 1. Otherwise, the charging equipment assumes that the firstsecondary battery 1 is fully charged, and stops charging the firstsecondary battery 1. At this time, the battery switching part 28receives a signal for finishing charging from the control part 26 andswitches a target connected to the charging circuit from the firstsecondary battery 1 to the next uncharged secondary battery 1, and thecharging equipment charges the next secondary battery 1 according to thesame charge control flow. In this way, the charging equipment repeatsthis charge control flow till all of the N secondary batteries 1 arefully charged.

The standard value K is a difference between the special chargingvoltage E_(s) and the open-circuit voltage E_(x) of the fully chargedsecondary battery 1, i.e., the equilibrium voltage E_(eq)(K=E_(s)−E_(eq)).

The control flow of charging the secondary battery 1 by the chargingequipment of the eleventh embodiment will be explained referring to theflow chart shown in FIG. 26.

To give an example of charging, the charging equipment of the tenthembodiment charges N secondary batteries 1.

First of all, a counter variable m (m=0, 1, 2, . . . N) designating thenumber of the charged secondary batteries 1 is initialized to 0 [stepS1].

Next, m+1 is substituted for the counter variable m [step S2], and thecontrol step goes to the next step S3. At the step S3, a usermanipulates the operation part (not shown) of the charging equipment tostart charging. Accordingly, the special charging voltage E_(s) higherthan the equilibrium voltage E_(eq) is applied to the secondary battery1 set in the charging equipment for a determined time T₁ [step S4].

After the determined time T₁ passes, the charging equipment breaks offapplication of the special charging voltage E_(s) for a time T₄ [stepS5]. In the meanwhile, the voltage detection part detects open-circuitvoltage E ((E_(α), E_(β), E_(γ), E_(δ), etc.) of the first secondarybattery 1 [step S6].

The voltage difference ΔE_(s) between the special charging voltage E_(s)and the open-circuit voltage E_(x) is computed [step S7]. The chargingequipment compares the computed voltage difference ΔE_(s) with thestandard value K [step S8]. If the voltage difference ΔE_(s) is largerthan the standard value K, the control step returns to the step S4, andthe charging equipment further applies the special charging voltageE_(s) to the secondary battery 1, and the above-mentioned charge controlsteps are repeated.

On the other hand, if the voltage difference ΔE_(s) is not larger thanthe standard value K, the charging equipment assumes that the secondarybattery 1 is fully charged, and the control step goes to the step S9. Atthe step S9, the count program judges whether the turn of the presentlycharged secondary battery 1 is the final Nth or not.

If the presently charged secondary battery 1 is not the Nth charged one,the control step goes to the next step S10. At the step S10, the batteryswitching part 28 switches a target connected to the charging circuitfrom the just fully charged secondary battery 1 to the next unchargedsecondary battery 1, the control steps returns to the step S2, and theabove-mentioned control steps are repeated.

On the other hand, if the presently charged secondary battery 1 is theNth charged one, the charging equipment assumes that all of thesecondary batteries 1 are fully charged, and it stops charging [stepS11].

Incidentally, the charging time T₁ for applying the special chargingvoltage E_(s) varies according to the capacity, structure, form, oranother element of each secondary battery 1. For example, for an AAnickel-cadmium battery or an AA nickel-hydrogen battery, the chargingtime T₁ is set to a time between 60 seconds and 90 seconds, and thebreak-off time T₄ is set to the time between 1 second and 5 seconds. Thetime required for voltage between terminals of the secondary battery 1to become stable and measurable is determined as the break-off time T₄.The break-off time T₄ for the AA nickel-cadmium battery or the AAnickel-hydrogen battery is set to a time between 1 second and 5 seconds.

The charging equipment needs to be designed for controlling charge ofthe secondary battery 1 so that the open-circuit voltage E_(x) should bedetected in the high impedance state where electric current does notflow through the target for measuring, such as the state where electriccurrent does not flow through the secondary battery 1 to which theequilibrium voltage is applied. Explanation of other structures, actionand effect of the charging equipment of the eleventh embodiment isomitted because they are substantially similar with those of thecharging equipment of the tenth embodiment.

TWELFTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERIES

A charging equipment for a plurality of secondary batteries 1 accordingto the twelfth embodiment of the present invention will be explained.

FIG. 27 is a block diagram of the charging equipment for a plurality ofsecondary batteries 1 according to the twelfth embodiment. The chargingequipment of the twelfth embodiment charges each of secondary batteries1, which are packed together in a packed power supply 40. The packedpower supply 40 has a plurality of battery groups 41 (as for the FIG.27, two battery groups 41) mutually connected in parallel. Each of thebattery groups 41 has a plurality of secondary batteries 1 mutuallyconnected in series.

In consideration of the above-mentioned characteristic of the secondarybatteries 1 in charging, the charging equipment of the twelfthembodiment is so configured as to charge the secondary batteries 1rapidly without damaging them. In detail, when this charging equipmentcharges each secondary battery 1, the special charging voltage E_(s)higher than the equilibrium voltage E_(eq) is applied to the secondarybattery 1 so as to supply high electric current to it for a determinedtime T₁, and then, voltage applied to the secondary battery 1 isswitched to the check voltage E_(c) lower than the special chargingvoltage E_(s), and the check voltage E_(c) is applied to the secondarybattery 1 for a short time T₃. The equilibrium voltage E_(eq) preferablyserves as the check voltage E_(c).

Then, the charging equipment detects electric current i flowing throughthe secondary battery 1 during application of the check voltage E_(c) tothe secondary battery 1, and compares the electric current i with presetstandard electric current J for finishing charging (electric currentassumed to be detected when charging is finished). If the detectedelectric current i is larger than the standard electric current J forfinishing charging, the charging equipment applies the special chargingvoltage E_(s) to the secondary battery 1 again. Otherwise, the chargingequipment assumes that the secondary battery 1 is fully charged, andstops charging the secondary battery 1.

To realize the above-mentioned charge control, the charging equipment ofthe twelfth embodiment is formed as shown in FIG. 27.

In detail, the charging equipment of the twelfth embodiment comprises apower supply part 42, a charging voltage control part 43, a checkvoltage control part 44, a processor (control part) 48, and the like.The power supply part 42 includes a transformer-rectifier circuit forchanging commercial alternating current into direct current. Theprocessor 48 transmits commands to a switch 46 so that the switch 46selects applied voltage between charging voltage and check voltageaccording to charging time and check time, whereby each battery group 41is supplied selectively with either the charging voltage by the chargingvoltage control part 43 or the check voltage (applied voltage forchecking the charged condition of the secondary battery 1) by the checkvoltage control part 44. A current detection part 47 (a detection partfor detecting electric current etc. flowing through the secondarybattery 1 during the application of the check voltage) transmits asignal about the electric current detected by the current detection part47 to the processor 48 during the check time. The processor 48repeatedly outputs either the command for charging the secondary battery1 or the command for checking the secondary battery 1 to the switch 47as far as the current detection part 47 detects any electric current.When the processor 48 detects that the present charging of the secondarybattery 1 is finished (for example, the processor 48 judges whether thedetected electric current is larger than the standard electric current Jfor finishing charging or not), the processor 48 commands the chargingequipment to apply voltage to the next secondary battery 1 as discussedlater. A display part 49 as an example of informational means receives aconditional signal from the packed power supply 40 and the processor 48,and displays information such as the charged condition of the packedpower supply 40 to decide whether the packed power supply 40 is fullycharged or not. The display part 49 may comprise LED, LCD, or the like.

The packed power supply 40 has the first circuit 91 for supplyingcharging voltage to each secondary battery 1 in one battery group 41marked with a reference numeral 101 in FIG. 27, and the second circuit92 for supplying charging voltage to each secondary battery 1 in theother battery group 41 marked with a reference numeral 102 in FIG. 27.

The first circuit 91 has transistors Tr consisting of A₁₁, A₁₂, . . .A_(1n), and transistors Tr consisting of B11, B₁₂, . . . B_(1n). Thesecond circuit 92 has transistors Tr consisting of A₂₁, A₂₂, A_(2n), andtransistors Tr consisting of B₂₁, B₂₂, . . . B_(2n).

Accordingly, the processor 48 as a control part can control transistorsTr consisting of A₁₁, A₁₂, . . . A_(1n) and transistors Tr consisting ofB₁₁, B₁₂, . . . B_(1n), on the first circuit 91 in one battery group 41,and control transistors Tr consisting of A₂₁, A₂₂, . . . A_(2n) andtransistors Tr consisting of B₂₁, B₂₂, . . . B_(2n) on the secondcircuit 92 in the other battery group 41. Additionally, the processor 48may control transistors Tr of the third through the nth circuits if theyare provided.

This charging equipment charges the secondary batteries 1 in eachbattery group 41 one by one.

A case that the charging equipment charges the battery group 41 markedwith the reference numeral 101 shown in FIG. 27 will be explained. Forinstance, when the charging equipment charges a secondary battery 1marked with a numeral reference II in this battery group 101, theprocessor 48 transmits “Hi” signal to each of the transistors A₁₂ andB₁₂, thereby supplying charge of electricity to the secondary batteryII. During charge of the secondary battery II, each transistor Tr otherthan the transistors A₁₂ and B₁₂ is in a state of “Low”. When thesecondary battery II is fully charged, the transistors A₁₃ and B₁₃receive “Hi” signal from the processor 48 so as to charge the nextsecondary battery 1 marked with a reference numeral III.

The state that any of the transistors Tr receives the “Hi” signal fromthe processor 48 means that after applying the special charging voltageE_(s) higher than the equilibrium voltage E_(eq) to the secondarybattery 1 so as to charge high electric current for a determined timeT₁, the charging equipment switches voltage applied to the secondarybattery 1 from the special charging voltage E_(s) to the check voltageE_(c), and applies the check voltage E_(c) to the secondary battery 1for a short time T₃.

Therefore, when the charging equipment finishes charging a secondarybattery 1, by command from the processor 48, the first circuit 91 isseparated from the just fully charged secondary battery 1 and connectedto the next uncharged secondary battery 1, and the charging equipmentcharges the next uncharged secondary battery 1 according to the samecharge control cycle. In this way, the charging equipment repeats thischarge control cycle till all of M secondary batteries 1 in the batterygroup 101.

When finishing charging all the secondary batteries 1 in the batterygroup 101 in FIG. 27, the charging equipment switches a battery group 41to be charged from the battery group 101 to the battery group 102 shownin FIG. 27, and charges each secondary battery 1 in the battery group102 one by one according to the same charge control cycle.

The control flow of charging the secondary batteries 1 by the chargingequipment of the twelfth embodiment will be explained referring to theflow chart shown in FIG. 28.

At first, charging of the battery group 101 shown in FIG. 27 will beexplained.

First of all, a counter variable p (p=0, 1, 2, . . . M) serving as thenumber of the fully charged secondary batteries 1 is initialized to 0[step T1]. Next, p+1 is substituted for the counter variable p [stepT2], and the control step goes to the next step T3. At the step T3, thecount program judges whether the number p of the fully charged secondarybatteries 1 reaches M or not. M is the number of all of the secondarybatteries 1 in the battery group 101.

At the step T3, if the counter variable p is not equal to M+1, thecontrol step goes to the next step T4. On the other hand, if the countervariable p is equal to M+1 (p=M+1), the charging equipment assumes thatall of the secondary batteries 1 in the battery group 101 are fullycharged, and it stops charging the battery group 101 [step T9].

In the case that the counter variable p isn't equal to M+1, the chargingequipment starts charging the pth secondary battery 1 and applies thespecial charging voltage E_(s) to the pth secondary battery 1 for adetermined time T₁ [step T5]. For instance, the charging time T₁ forapplying the special charging voltage E_(s) to the secondary battery 1is set to about 120 seconds.

After the determined time T₁ passes, the charging equipment switchesapplied voltage from the special charging voltage E_(s) to the checkvoltage E_(c) (e.g. the equilibrium voltage E_(eq)) [step T6]. Thecurrent detection part 47 detects electric current i flowing through thepth secondary battery 1 during the application of the check voltageE_(c) to the pth secondary battery 1 for a short time T₃ [step T7]. Forexample, the short time T₃ for applying the check voltage E_(c) to thesecondary battery 1 is set to about 0.1 second.

At the step T8, the check current judging program compares the detectedvalue of electric current i with standard electric current J forfinishing charging (electric current assumed to be detected whencharging is completed). If the detected electric current i is largerthan the standard electric current J for finishing charging, the controlstep returns to the step T4, and the charging equipment applies thespecial charging voltage E_(s) to the secondary battery 1, and repeatsthe above-mentioned charge control steps. Otherwise, the chargingequipment assumes that the pth secondary battery 1 is fully charged, andthe control step returns to the step T2, which means that the chargingequipment finishes charging the pth secondary battery 1.

In this way, the charging equipment repeats the above-mentioned chargecycle so as to fully charge all of the secondary batteries 1 of thebattery group 101 [step T9].

Incidentally, the equilibrium voltage E_(eq) is suitable for serving asthe check voltage for easily judging whether the secondary battery 1 isfully charged or not, because the electric current becomes almost 0 mAwhen its charging rate reaches 100% (the fully charged condition), asunderstood from the graph showing in FIG. 3. However, even if thesecondary batteries 1 are identical in classification, the equilibriumvoltage E_(eq) of each secondary battery 1 is slightly different fromone another. To prevent overcharging in consideration of such situation,the standard voltage J for finishing charging is desirably set to beabout 10 mA, for example, considerably higher than 0 mA. When thecharging equipment starts charging the secondary battery 1 at the stepT4, the display part 49 starts to display that the packed power supply40 is under charging.

When finishing charging all of the secondary batteries 1 of the batterygroup 101, the charging equipment starts charging secondary batteries 1of the next battery group 41 (102). In other words, when finishingcharging the battery group 101, the charging equipment should judge thatthe variable p equals M+1 (p=M+1) at the step T₃ shown in FIG. 28.Therefore, when p is equal to M+1, the processor 48 commands to startcharging the battery group 102.

The charging equipment charges the battery group 102 according to thesimilar control flow for charging the battery group 101. If the chargingequipment finishes charging both the battery groups 101 and 102, thedisplay part 49 switches its indication from about under charging toabout finishing charging.

According to the twelfth embodiment, the charging equipment checks thecharged condition of the secondary battery 1 periodically by detectingelectric current i flowing through the secondary battery 1. By thischarging method, each secondary battery 1 is fully charged appropriatelywithout causing excessive damaging chemical reaction(oxidation-reduction reaction) therein, thereby remarkably increasingeffective battery cycles of the secondary batteries 1.

Additionally, this charging method supplies each of the secondarybatteries 1 with pretty large charging current by mainly applying thespecial charging voltage E, larger than the equilibrium voltage E_(eq)to the secondary battery 1, thereby reducing charge time.

The charging equipment charges the secondary batteries 1 one by one,thereby surely fully charging all of the secondary batteries 1. Eachbattery group 41 is prevented from being finished in its charging whilean insufficiently charged secondary battery 1 remains therein, therebyenhancing its reliability.

Moreover, the charging equipment starts charging the battery groups 102after it finishes charging the battery group 101. Then, the chargingequipment finishes charging the battery group 102, thereby fullycharging all of the secondary batteries 1 in the packed power supply 40appropriately for a short time. Therefore, the secondary batteries 1fully charged by the charging equipment increase their effective batterycycles.

The display part 49 indicates the charged condition of each packed powersupply 40, that is, either under charging or fully charged, therebyfacilitating for users' monitoring the charged condition of the packedpower supply 40. The user, when noticed from the display part 49 thatthe packed power supply 40 is fully charged, can immediately use thepacked power supply 40 for driving any kind of load. The display part 40may have two lights in different colors such that one light is turned onwhen the packed power supply 40 is under charging, and the other isturned on when charging of the packed power supply 40 is finished.Alternatively, the display part 40 may have only one light, which istuned on (or turned off) when the packed power supply 40 is undercharging, and turned off (or turned on) when charging of the packedpower supply 40 is finished. Further alternatively, the display part 49may selectively display either literal sign “Under Charging” or“Charging Is Finished”.

This charging equipment comprises the display part 49 as an example ofan information means which indicates the charged condition of the packedpower supply 40 to a user through his/her eyes, however, the chargingequipment may have any other information means for informing a user withsound or the like.

For charging a packed power supply 40 including a plurality of batterygroups 41, the charging equipment of the twelfth embodiment, as shown inFIG. 27, starts charging the uncharged battery group 41 after finishingcharging the next battery group 41 ahead. Alternatively, the chargingequipment may be configured so as to charge the plurality of batterygroups 41 simultaneously. This charging equipment may start charging allof the battery groups 41 simultaneously, so as to finish charging themapproximately simultaneously, thereby remarkably reducing the totalcharging time. The timings for starting charging the respective batterygroups 41 may be different from one another to some degree. For example,the charging equipment may start charging the second battery group 102(in FIG. 27) after the passage of the determined time from the momentwhen starting charging the first battery group 101 (in FIG. 27) (beforethe moment when finishing charging the battery group 101). Furtheralternatively, the charging equipment may start charging the secondbattery group 102 not immediately but after the passage of thedetermined time from the moment when finishing charging the firstbattery group 101.

The packed power supply 40 having a plurality of battery groups 41 (101and 102) may be made usable in any of the following modes: In one mode,either the battery group 101 or 102 is selectively connected to load. Inanother mode, the battery groups 101 and 102 are connected in parallelto load, and in another mode, the battery groups 101 and 102 areconnected in series to load. The packed power supply 40 preferably hassuch flexibility as to correspond to various kinds of load. In thiscase, the packed power supply 40 has switching means in its circuit soas to selectively connect the battery groups 101 and 102 either inseries or in parallel to load.

Incidentally, the necessary time t to fully charge the secondary battery1 (i.e. the charge time) can be calculated basing on the graph of FIG. 4showing the relation between the electric current i and the necessarytime t. This graph shows the relation between the detected electriccurrent i during the application of the equilibrium voltage E_(eq) andthe necessary time t to fully charge the secondary battery 1. On theassumption that I_(eqo) (referring to FIG. 3) serves as the detectedelectric current i during the application of the equilibrium voltageE_(eq) to the secondary battery 1 whose charging rate is 0%, this graphshows that the higher the charging rate is, the shorter the necessarytime t is and the smaller the detected electric current i is. In thisgraph, when the detected electric current i reaches 0 mA, the secondarybattery 1 is fully charged so that the charging rate becomes 100% andthe necessary time t becomes 0.

Therefore, the charge time predicting program basing on this graph ispreferably programmed in the processor 48 serving as the control means,thereby enabling the necessary time t for fully charging the secondarybattery 1 to be estimated basing on the detected electric current i.Accordingly, the charging equipment may stop charging the secondarybattery 1 after the passage of the necessary time t which is computed bythe charge time predicting means, i.e., the charge time predictingprogram. The detected necessary time t to fully charge the secondarybattery 1 may be preferably indicated as the charging time t on thedisplay part 49. By indicating the displayed charging time t, a user canknow when the charging will be finished.

The charging equipment of the twelfth embodiment may be modified withoutdeparting from the scope of attended claims. For instance, the number ofthe battery groups 41 in the packed power supply 40 may be increased ordecreased freely. Also, the number of the batteries 1 of each batterygroup 41 may be increased or decreased freely. When the chargingequipment charges each secondary battery 1, it may short-circuit thesecondary battery 1 between its terminals for an extremely short time(e.g. about 0.001 second) before it applies the check voltage E_(c) tothe secondary battery 1. The short-circuiting can clear electricity fromthe electrode interface of the secondary battery 1, so that appliedvoltage to the secondary battery 1 can be smoothly switched from thecharging voltage to the check voltage E_(c), and charging electriccurrent is stabilized just after switching applied voltage to the checkvoltage E_(c), whereby electric current i can be accurately detected andthe secondary battery 1 can be charged appropriately.

For finishing charging a secondary battery 1, the charging rate of thesecondary battery 1 at the time when detecting the electric current imay be calculated basing on the detected electric current i by using thegraph of FIG. 3, and charging of the secondary battery 1 may bealternatively stopped when its charging rate reaches a determined value.

When the charging equipment charges each secondary battery 1, it mayalternatively detect open-circuit voltage E_(x) of the secondary battery1.

In this case, the charging equipment detects the voltage differenceΔE_(s) between the special charging voltage E_(s) and the open-circuitvoltage E (E_(α), E_(β), E_(γ), E_(δ), etc.) of the second battery 1,and compares the open-circuit voltage E with the preset standard valueK. If the voltage difference ΔE_(s) is larger than the standard value K,it may continue charging the secondary battery 1; otherwise, it may stopcharging the secondary battery 1. The standard value K is a differencebetween the special charging voltage E_(s) and the open-circuit voltageE of the secondary battery 1 in its fully charged condition, that is,the open-circuit voltage E is equal to the equilibrium voltage E_(eq)(K=E_(s)−E_(eq)). In this case, the charging equipment can compute thenecessary time t to fully charge the secondary battery 1, basing on thedetected voltage difference ΔE_(s) between the equilibrium voltageE_(eq) and the open-circuit voltage E_(x), and it can indicate thenecessary time t on the display part 49.

When charging is finished, the display part 49 may sound (with a buzzer,for example) to inform a user that charge of the secondary battery 1 isfinished. If a plurality of battery groups 41 are provided, the displaypart 49 may indicate not only the state of finishing charging all of thebattery groups 41, but also the state of finishing charging each batterygroup 41. If power of only one battery group 41 is sufficient fordriving load, the power supply may be conveniently used immediatelyafter the display part 49 notices that one of the battery group 41 iscompletely charged, without waiting for charging another battery group41.

THIRTEENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to thethirteenth embodiment of the present invention will be explained.

The fully charged secondary battery 1, if remaining unused, naturallyself-discharges so as to reduce its voltage gradually. For example, incase the secondary battery 1 is left unused for two days, almost 15%voltage falls. In case for thirty days, almost 40% voltage falls. Forthis reason, when the secondary battery 1 is set in load such as digitalcamera, its voltage may be so low that the load does not work well.

To solve this problem, the charging equipment of the thirteenthembodiment recharges a fully charged secondary battery 1 when voltage ofthe fully charged secondary battery 1 falls lower than the predeterminedvalue. The manner for recharging the secondary battery 1 may be any ofthe above-mentioned charging manners employed by the charging equipmentsof the first to twelfth embodiments, or another charging manner.

The charging equipment of the thirteenth embodiment is configuredsimilarly with that shown in FIG. 1. The control part 4 has a rechargejudging program serving as means for judging whether voltage of thecharged secondary battery detected by the voltage detection part 9 islarger than the recharging voltage E_(r) smaller than the equilibriumvoltage E_(eq) or not.

For instance, the recharging voltage E_(r) is set to 80% of theequilibrium voltage E_(eq). The battery voltage of the secondary battery1 remaining set in the charging equipment is always observed by thevoltage detection part 9 even after charge of the secondary battery 1 isfinished. When the observed battery voltage of the secondary battery 1becomes not larger than the recharging voltage E_(r), the control part 4outputs command for recharging to the charging voltage supply part 6,which supplies charging voltage to the secondary battery 1. Thus, thecharging equipment recharges the secondary battery 1.

Whether this charging equipment employs the charging manner of any ofthe first to twelfth embodiments or another charging manner, recharge ofthe secondary battery is finished by the charge-finishing process in theemployed charging manner.

By recharging as mentioned above, the battery voltage of the secondarybattery 1 picked out from the charging equipment is always not smallerthan the recharging voltage E_(r). In other words, conveniently, thesecondary battery 1 set in the charging equipment always stands by inthe state of being suitable for use.

Also, in the process of recharging, such excessive chemical reaction(oxidation-reduction reaction) as to damage the internal structure ofthe secondary battery does not occur in the secondary battery, wherebythe secondary battery 1 is recharged appropriately till its fullycharged condition, thereby increasing its effective battery cycles.

FOURTEENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERIES

A charging equipment for a plurality of secondary batteries 1 accordingto the fourteenth embodiment of the present invention will be explained.

FIG. 29 is a plan view of the charging equipment for charging aplurality of (in this embodiment, four) secondary batteries 1 accordingto the fourteenth embodiment.

Referring to FIG. 29, a reference numeral 50 a designates a seat ontowhich a secondary battery 1 is set, a reference numeral 50 b designatesan air intake for taking in the open air, and a reference numeral 51designates a first display part, which is lighted on when the secondarybattery 1 is nearly fully charged. For example, the first display part51 is turned on when battery voltage of the secondary battery 1 reachesthe recharging voltage E_(r). Such designed charging equipment startsrecharging the secondary battery 1 after the lighting first display part51 is lighted off so as to notice charge of the secondary battery 1 isfinished. A reference numeral 52 designates each of second display partscorresponding to the respective secondary batteries 1. The secondarybatteries 1 are charged one by one in order as a bold arrow shown inFIG. 29. Each of the second display parts 52 is lighted on when thecorresponding secondary battery 1 is under charging. A reference numeral53 designates a take-off button for taking off the secondary battery 1from the seat 50 a, a reference numeral 54 designates a start button forstarting charging the secondary batteries 1, and a reference numeral 55designates a pilot lump. The charging equipment 50 is connected to thecommercial power source by a cord (not shown in FIG. 29).

The charging equipment 50 of the fourteenth embodiment performs chargingoperation for each of the secondary batteries 1 so as to fully chargethe plurality of secondary batteries 1 set therein one by one in orderas the bold arrow in FIG. 29. In each charging operation, the chargedcondition of the secondary battery 1 is checked and the secondarybattery 1, if it is not fully charged, is charged by application ofpredetermined charging voltage for a determined time. A series of thecharging operations for all the secondary batteries 1 designates onecharging turn. The charging equipment repeats the charging turn, whereinif any of the secondary batteries 1 is judged to be fully charged, it isput off charging.

If any of the secondary batteries 1 is full charged, the chargingoperation for the fully charged secondary battery 1 is skipped at thenext charging turn.

In each charging turn, the order of charging operations for thesecondary batteries 1 is not limited to that as drawn in the bold arrowin FIG. 29. The charging operations in each charging turn may beperformed in other order.

The above-mentioned check in charging operation for each secondarybattery 1 is made by judgment of the electric current i at the step A8in the first embodiment, or the judgment of the voltage differenceΔE_(s) at the step G7 in the fourth embodiment, for example. Theabove-mentioned predetermined charging voltage to be applied to thesecondary battery 1 is set to the special charging voltage E_(s), forexample.

The charging equipment 50 halts charging each of secondary batteries 1between the final charging operation in a charging turn and the firstcharging operation in the next charging turn. This halting term isrelaxation time for the secondary batteries. For this term, the surfaceof the electrode of each secondary battery 1 is stabilized so that thecharging equipment 50 can accurately check the charged condition of thesecondary battery 1 whether it is fully charged or not, thereby beingimproved in reliability.

Complementarily speaking, in the process of charging a secondary battery1, electrode reaction occurs on an electrode surface touchingelectrolyte. In this electrode reaction are simultaneously performedmovement of reactant to the electrode surface from the electrolyte,movement of electron between the reactant and the electrode, andmovement of product into the electrolyte from the electrode surface. Ittakes quite a long time for these movements so that the secondarybattery 1, if the charged state thereof is checked immediately afterpausing charge of the secondary battery, may be misread as if it reachedthe fully charged condition because of ion and the like beingelectrophoresed around the electrode surface. The relaxation time isadvantageous for preventing such misreading. The charging equipment ofthe fourth embodiment rationally and effectively sets the relaxationtime as a partial process in a cycle of charging each of secondarybatteries 1.

Each of the charging equipments according to the first to twelfthembodiments may establish the relaxation time for each secondary battery1 after its charging for a determined time T₁ and before check of itscharged condition.

FIFTEENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to thefifteenth embodiment of the present invention will be explained.

Referring to FIG. 30, the charging equipment 50 of the fifteenthembodiment comprises a cooling fan 61 serving as cooling means. Theequipment 50 of the fifteenth embodiment charges the secondary battery 1without causing excessive chemical reaction therein by any of theabove-mentioned methods employed by the charging equipments according tothe first to fourteenth embodiments, thereby preventing the secondarybattery 1 from generating heat by itself. However, in the chargingequipment 50, electronic components, such as resistors, for controllingcharge are exothermic. The cooling fan 61 is provided for cooling theexothermic components 64 and 65 such as resistors and the like.

In FIG. 30, a reference numeral 50C designates a casing of the chargingequipment 50, a reference numeral 50 b designates an air intake fortaking in the open air made in a top surface of the casing 50C(referring to FIG. 29) adjacent to one side, a reference numeral 50 ddesignates an air intake for taking in the open air made on a bottomsurface of the casing 50C adjacent to the side, a reference numeral 50 edesignates an air outlet made on another bottom surface of the casing50C adjacent to the other side, and a reference numeral 50 h designateseach of feet for supporting the casing 50C. Reference numerals 62 and 63designate substrates, and reference numerals 64 and 65 designateexothermic components such as resistors.

The charging equipment 50 drives the cooling fan 61 so as to inhale theopen air into the casing 50C through both the air intakes 50b and 50 dadjacent to one side. The inhaled air is drifted along surfaces of theexothermic components 64 and 65, thereby cooling the exothermiccomponents 64 and 65. The cooling fan 61 drifts the inhaled air drifttoward the other side of the casing 50C, and exhausts it through the airoutlet 50 e.

The charging equipment 50 having the above-mentioned structure preventsthe exothermic components 64 and 65 from generating heat, which may betransferred to the secondary battery 1 so as to promote excessivechemical reaction (oxidation-reduction reaction) therein. A user isprevented from such illusion that the secondary battery 1 runs atemperature. Consequently, the charging equipment charges the secondarybattery 1 appropriately without damaging its internal structure till thefully charged condition of the secondary battery 1, thereby remarkablyincreasing effective battery cycles of the secondary battery 1.

SIXTEENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to thesixteenth embodiment of the present invention will be explained.

The charging equipment 50 of the sixteenth embodiment comprises atake-off means for taking off the secondary battery 1 set on thecharging equipment 50 by one-touch operation. Referring to FIG. 29 andFIG. 30, the take-off means of the charging equipment 50 of thesixteenth embodiment comprises a take-off button 53, a boost member 57for pushing up the secondary battery 1 set on the seat 50 a of thecharging equipment 50, a shaft 58 for rotatably supporting the boostmember 57, and a torsion spring 59 attached to the shaft 58 forenergizing the boost member 57 opposite to the movement of the boostmember 57 when pushed up.

In this structure, as shown in FIG. 31( b), when a user pushes down thetake-off button 53 serving as operation member, the bottom of thetake-off button 53 pushes down one side of the boost member 57, and theboost member 57 pivots on the shaft 58 and arises at the other sidethereof above the seat 50 a so as to push up the secondary battery 1,thereby releasing terminals of the secondary battery 1.

When the take-off button 53 is released from a user's finger, therestoring force of the torsion spring 59 serving as energization meansreturns the rising side of the boost member 57 to the initial position,where this side of the boost member 57 is fit along a curved surface ofthe seat 50 a, whereby the seat 50 a is ready to receive a secondarybattery 1.

In short, when a user operates the take-off button 53, one side of theboost member 57 moves above the seat 50 a so as to release terminals ofthe secondary battery 1 set on the seat 50 a. Due to this convenientstructure, a user can take off the secondary battery 1 set on thecharging equipment 50 easily by one-touch operation.

SEVENTEENTH EMBODIMENT OF CHARGING EQUIPMENT FOR SECONDARY BATTERY

A charging equipment for a secondary battery 1 according to theseventeenth embodiment of the present invention will be explained.

The charging equipment 50 of the seventeenth embodiment comprises atake-off means other than the take-off means of the charging equipment50 of the sixteenth embodiment.

As shown in FIG. 32, in the charging equipment 50 of the seventeenthembodiment, the seat 50 a is formed at one side portion of the seat 50 ain its longitudinal direction with a downward recess 50 k so that thebottom of the secondary battery 1 set on the seat 50 a is disposed abovethe recess 50 k.

As shown in FIGS. 32( a) and 32(b), one side of secondary battery 1 ispushed down by a user into the recess 50 k, so that the other side ofthe secondary battery 1 rises above the seat 50 a, thereby releasingterminals of the secondary battery 1. In this way, a user canconveniently take off the secondary battery 1 by one-touch operation.

The foregoing explanation of the charging equipments according to thefirst to seventh embodiments are provided as only preferred embodimentsof the present invention. Each of the foresaid charging equipment ormethod may be modified or changed within the scope of attended claims.

As for the above-mentioned charging equipment shown in FIG. 1 accordingto the first and other embodiments, the necessary time t to fully chargethe secondary battery 1 is calculated. Alternatively, the charging rateof the secondary battery 1 may be calculated basing on the detectedelectric current i by using the graph shown in FIG. 3 or the like, andcharging of the secondary battery 1 may be stopped when the chargingrate reaches a predetermined value.

Referring to the flow chart shown in FIG. 5, the step A7 for calculatingthe charging time t may be omitted because, in the charging flow shownin FIG. 5, judgment of the charged condition of the secondary battery 1whether its charging is to be finished or not is enabled to depend oncomparison of the detected electric current i with the preset standardelectric current J for finishing charging.

As for the charging equipment of each embodiment, after the specialcharging voltage E_(s) larger than the equilibrium voltage E_(eq) isapplied for a determined time T1, applied voltage is switched from thespecial charging voltage E_(s) to the equilibrium voltage E_(eq).Alternatively, the special charging voltage E_(s) may be continuouslyapplied without switching voltage, and the necessary time t to fullycharge the secondary battery 1 may be calculated basing on the detectedelectric current i.

Incidentally, in the charging equipment of each embodiment, theterminals of the secondary battery 1 may be short-circuited beforevoltage applied to the secondary battery 1 from the special chargingvoltage E_(s) to the equilibrium voltage E_(eq), thereby desirablyremoving electricity from the electrode interface of the secondarybattery 1 so as to smoothen switch of voltage from the charging voltageto the equilibrium voltage E_(eq), and stabilize the electric currentflowing through the secondary battery 1 immediately after change to theequilibrium voltage E_(eq). Alternatively, the charging equipment mayswitch voltage without short-circuiting the secondary battery 1.

1. A charging equipment for a secondary battery, comprising: a voltagesupply means for applying voltage to the secondary battery; a currentdetection means for detecting electric current flowing through thesecondary battery; and a charge control device for controlling charge ofthe secondary battery, the charge control device including a storagemeans storing equilibrium voltage and special charging voltagecorresponding to the secondary battery to be charged, the equilibriumvoltage for establishing equilibrium cell potential of the secondarybattery in a fully charged condition, and the special charging voltagefor supplying the secondary battery with charging electric current ofpeak or almost peak value, wherein the special charging voltage islarger than the equilibrium voltage and does not reach a region ofvoltage causing irreversible chemical reaction in the secondary battery,a switching means for switching charging voltage supplied by the voltagesupply means between the equilibrium voltage and the special chargingvoltage, and a judging means for judging whether electric currentdetected by the current detection means during application of theequilibrium voltage is larger than a preset standard electric currentfor finishing charging or not, wherein the charge control devicecontrols charge of a secondary battery by first to fourth steps: thefirst step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time; thesecond step of switching charging voltage applied to the secondarybattery from the special charging voltage to the equilibrium voltage;the third step of detecting electric current flowing through thesecondary battery by the current detection means while applying theequilibrium voltage to the secondary battery for a short time; and thefourth step of returning to the first step and repeating the above stepsif the judging means judges that the detected electric current is largerthan the standard electric current for finishing charging; otherwise,halting the secondary battery.
 2. A charging equipment for a secondarybattery according to claim 1, wherein the storage means of the chargecontrol device previously stores the equilibrium voltages and thespecial charging voltages for charging various kinds of secondarybatteries, and wherein data of a kind of secondary battery to be chargedis inputted to the charge control device so that the equilibrium voltageand the special charging voltage in correspondence to the kind ofsecondary battery are selected from a table of the storage means so asto charge the kind of secondary battery basing on the selectedequilibrium voltage and special charging voltage.
 3. A chargingequipment for a secondary battery according to claim 1 or 2, furthercomprising: a short-circuit means for short-circuiting the secondarybattery between its terminals after applying the special chargingvoltage for the predetermined time and before switching charging voltageto the equilibrium voltage.
 4. A charging equipment for a secondarybattery according to claim 1, further comprising: a cooling means forcooling an exothermic section in the charging equipment.
 5. A chargingequipment for a secondary battery, comprising: a voltage supply meansfor applying voltage to the secondary battery; a current detection meansfor detecting electric current flowing through the secondary battery; avoltage detection means for detecting voltage applied to the secondarybattery; and a charge control device for controlling charge of thesecondary battery, the charge control device including a storage meansstoring n (n is a natural number larger than 1) equilibrium voltages andn special charging voltages for charging n kinds of secondary batteries,each of the equilibrium voltages for establishing equilibrium cellpotential of the secondary battery in a fully charged condition, andeach of the special charging voltages for supplying the secondarybattery with charging electric current of peak or almost peak value,wherein each of the special charging voltages is larger than thecorresponding equilibrium voltage and does not reach a region of voltagecausing irreversible chemical reaction in the corresponding secondarybattery; a switching means for switching charging voltage supplied bythe voltage supply means; a current judging means for judging whetherelectric current detected by the current detection means duringapplication of charging the equilibrium voltage is larger than a presetstandard electric current for finishing charging or not; and a voltagejudging means for judging whether voltage detected by the voltagedetection means during application of charging voltage of thepredetermined value is larger than the special charging voltage or not,wherein the charge control device controls charge of a secondary batteryby first to eighth steps: the first step of initializing a countervariable k (k1 ,2, . . . , n) to 1; the second step of applying the kthsmallest voltage of the n special charging voltages to the secondarybattery set in the charging equipment for a predetermined time; thethird step to jumping to the sixth step if k is equal to n; the fourthstep of detecting voltage applied to the secondary battery by thevoltage detection means while applying the kth smallest special chargingvoltage to the secondary battery for the predetermined time; the fifthstep of incrementing the rank of k by 1 and returning to the second stepif the voltage judging means judges that the detected voltage is largerthan the kth smallest special charging voltage; otherwise, passing tothe sixth step; the sixth step of switching charging voltage applied tothe secondary battery to the kth smallest voltage of the n equilibriumvoltages; the seventh step of detecting electric current flowing throughthe secondary battery by the current detection means while applying thekth smallest equilibrium voltage to the secondary battery for a shorttime; and the eighth step of returning to the second step and repeatingthe above steps if the current judging means judges that the detectedelectric current is larger than the standard electric current forfinishing charging; otherwise, halting charge of the secondary battery.6. A charging equipment for a secondary battery according to claim 5,further comprising: a short-circuit for short-circuiting the secondarybattery between its terminals after applying the special chargingvoltage for the predetermined time and before switching charging voltageto the equilibrium voltage.
 7. A charging equipment for a secondarybattery according to claim 5 or 6, further comprising: a cooling meansfor cooling an exothermic section in the charging equipment.
 8. Acharging equipment for a secondary battery, comprising: a voltage supplymeans for applying voltage to the secondary battery; a current detectionmeans for detecting electric current flowing through the secondarybattery; a voltage detection means for detecting voltage applied to thesecondary battery; and a charge control device for controlling charge ofthe secondary battery, the charge control device including a storagemeans storing n (n is a natural number larger than 1) equilibriumvoltages and n special charging voltages for charging n kinds ofsecondary batteries, each of the equilibrium voltages for establishingequilibrium cell potential of the secondary battery in a fully chargedcondition, and each of the special charging voltages for supplying thesecondary battery with charging electric current of peak or almost peakvalue, wherein each of the special charging voltages is larger than thecorresponding equilibrium voltage and does not reach a region of voltagecausing irreversible chemical reaction in the corresponding secondarybattery; a switching means for switching charging voltage supplied bythe voltage supply means; a current judging means for judging whetherelectric current detected by the current detection means duringapplication of the equilibrium voltage is larger than a preset standardelectric current for finishing charging or not, and a voltage differencejudging means for judging whether a difference of voltage detected bythe voltage detection means during application of the special chargingvoltage between a present value and a past value is within a presetrange or not, wherein the charge control device controls charge of asecondary battery by first to eighth steps: the first step ofinitializing a counter variable k (k=1,2, . . . , n) to 1; the secondstep of applying the kth smallest voltage of the n special chargingvoltages to the secondary battery set in the charging equipment for apredetermined time; the third step of jumping to the sixth step if k isequal to n; the fourth step of detecting voltage applied to thesecondary battery by the voltage detection means while applying the kthsmallest special charging voltage to the secondary battery for thepredetermined time; the fifth step of passing to the sixth step if thevoltage detection is the first time or the voltage difference judgingmeans judges that the detected voltage difference is within the range;otherwise, incrementing the rank of k by 1 and returning to the secondstep; the sixth step of switching charging voltage applied to thesecondary battery from the kth smallest special charging voltage to thekth smallest voltage of the n equilibrium voltages; the seventh step ofdetecting electric current flowing through the secondary battery by thecurrent detection means while applying the kth equilibrium voltage tothe secondary battery for a short time; and the eighth step of returningto the second step and repeating the above steps if the current judgingmeans judges that the detected electric current is larger than thestandard electric current for finishing charging; otherwise, haltingcharge of the secondary battery.
 9. A charging equipment for a secondarybattery according to claim 8, further comprising: a short-circuit forshort-circuiting the secondary battery between its terminals afterapplying the special charging voltage for the predetermined time andbefore switching charging voltage to the equilibrium voltage.
 10. Acharging equipment for a secondary battery according to claim 8 or 9,further comprising: a cooling means for cooling an exothermic section inthe charging equipment.
 11. A charging equipment for a secondarybattery, comprising: a voltage supply means for applying voltage to thesecondary battery; a voltage detection means for detecting open-circuitvoltage of the secondary battery; and a charge control device forcontrolling charge of the secondary battery, the charge control deviceincluding a storage means storing special charging voltage for supplyingthe secondary battery with charging electric current of peak or almostpeak value, wherein the special charging voltage is larger than voltagefor establishing equilibrium cell potential of the secondary battery ina fully charged condition and does not reach a region of voltage causingirreversible chemical reaction in the secondary battery, and a voltagedifference judging means for judging whether a voltage differencebetween the charging voltage and the open-circuit voltage of thesecondary battery is larger than a preset standard value or not, whereinthe charge control device controls charge of a secondary battery byfirst to third steps: the first step of applying the special chargingvoltage to the secondary battery set in the charging equipment for apredetermined time, and then shutting off the charging voltage from thesecondary battery; the second step of detecting the open-circuit voltageof the secondary battery by the voltage detection means, and computingthe voltage difference between the charging voltage of the specialcharging voltage and the open-circuit voltage of the secondary battery;and the third step of returning to the first step and repeating theabove steps if the voltage difference judging means judges that thecomputed voltage difference is larger than the standard value;otherwise, halting charge of the secondary battery.
 12. A chargingequipment for a secondary battery according to claim 11, furthercomprising: an informational means for giving information of the timerequired to charge the secondary battery, the charging rate of thesecondary battery, or a charged condition of the secondary battery fordeciding whether charge of the secondary battery is finished or not. 13.A charging equipment for a secondary battery according to claim 11 or12, further comprising: a cooling means for cooling an exothermicsection in the charging equipment.
 14. A charging equipment for asecondary battery, comprising: a voltage supply means for applyingvoltage to the secondary battery; a voltage detection means fordetecting open-circuit voltage of the secondary battery; and a chargecontrol device for controlling charge of the secondary battery, thecharge control device including a storage means storing equilibriumvoltage and special charging voltage corresponding to the secondarybattery to be charged, the equilibrium voltage for establishingequilibrium cell potential of the secondary battery in a fully chargedcondition, and the special charging voltage supplying the secondarybattery with charging electric current of peak or almost peak value,wherein the special charging voltage is larger than the equilibriumvoltage and does not reach a region of voltage causing irreversiblechemical reaction in the secondary battery, a judging means for judgingwhether the open-circuit voltage of the secondary battery detected bythe voltage detection means is larger than a standard voltage as theequilibrium voltage or not, wherein the charge control device controlscharge of a secondary battery by first to third steps: the first step ofapplying the special charging voltage to the secondary battery set inthe charging equipment for a predetermined time, and then shutting offthe charging voltage from the secondary battery; the second step ofdetecting the open-circuit voltage of the secondary battery by thevoltage detection means, and computing the voltage difference betweenthe special charging voltage and the open-circuit voltage of thesecondary battery; and the third step of returning to the first step andrepeating the above steps if the judging means judges that the detectedopen-circuit voltage is smaller than the equilibrium voltage as thestandard voltage; otherwise, halting charge of the secondary battery.15. A charging equipment for a secondary battery according to claim 14,further comprising: an informational means for giving information of thetime required to charge the secondary battery, the charging rate of thesecondary battery, or a charged condition of the secondary battery fordeciding whether charge of the secondary battery is finished or not. 16.A charging equipment for a secondary battery according to claim 14 or15, further comprising: a cooling means for cooling an exothermicsection in the charging equipment.
 17. A charging equipment for asecondary battery comprising: a voltage supply means for applyingpredetermined voltage to the secondary battery; a current detectionmeans for detecting a value of electric current flowing through thesecondary battery during application of the predetermined voltage to thesecondary battery; and a charge time predicting means for estimating atime required to fully charge the secondary battery basing on thedetected value of electric current, wherein the voltage supply meansapplies charging voltage, which is larger than the predeterminedvoltage, to the secondary battery for a predetermined time, and thenapplied voltage is switched to the predetermined voltage, and thecurrent detection means detects a value of electric current flowingthrough the secondary battery during application of the special chargingvoltage.
 18. A charging equipment for a secondary battery according toclaim 17, wherein the time required to fully charge the secondarybattery is a time for the electric current detected by the currentdetection means to reach standard electric current for finishingcharging, whereby charge of the secondary battery is halted when thedetected value of electric current is not larger than the standardelectric current for finishing charging.
 19. A charging equipment for asecondary battery according to claim 17, wherein the charging equipmenthalts charge of the secondary battery after the lapse of the timerequired to fully charge the secondary battery.
 20. A charging equipmentfor a secondary battery according to claim 17, wherein the predeterminedvoltage is equilibrium voltage for establishing equilibrium cellpotential of the secondary battery in a fully charged condition.
 21. Acharging equipment for a secondary battery according to claim 17,further comprising: an informational means for giving information of thetime required to fully charge the secondary battery, the charging rateof the secondary battery, or a charged condition of the secondarybattery for deciding whether charge of the secondary battery is finishedor not.
 22. A charging equipment for a secondary battery according toclaim 17, further comprising: a cooling means for cooling an exothermicsection in the charging equipment.
 23. A charging equipment for asecondary battery comprising: a voltage supply means for applyingspecial charging voltage to the secondary battery; a current detectionmeans for detecting electric current flowing through the secondarybattery during application of the special charging voltage to thesecondary battery; and a charging rate computing means for computing acharging rate of the secondary battery at the moment when the currentdetection means detects the electric current, wherein the voltage supplymeans applies charging voltage, which is larger than the specialcharging voltage, to the secondary battery for a predetermined time, andthen the charging voltage is switched to the special charging voltage,and the current detection means detects electric current flowing throughthe secondary battery during application of the special chargingvoltage.
 24. A charging equipment for a secondary battery according toclaim 23, further comprising: an informational means for givinginformation of the time required to fully charge the secondary battery,the charging rate of the secondary battery, or a charged condition ofthe secondary battery for deciding whether charge of the secondarybattery is finished or not.
 25. A charging equipment for a secondarybattery according to claim 23, further comprising: a cooling means forcooling an exothermic section in the charging equipment.
 26. A chargingequipment for a secondary battery, comprising: a voltage supply meansfor applying voltage to the secondary battery; a current detection meansfor detecting electric current flowing through the secondary battery;and a charge control device for controlling charge of the secondarybattery, the charge control device including a storage means storingequilibrium voltage and special charging voltage corresponding to thesecondary battery to be charged, the equilibrium voltage forestablishing equilibrium cell potential of the secondary battery in afully charged condition, and the special charging voltage for supplyingthe secondary battery with charging electric current of peak or almostpeak value, wherein the special charging voltage is larger than theequilibrium voltage and does not reach a region of voltage causingirreversible chemical reaction in the secondary battery, a switchingmeans for switching charging voltage supplied by the voltage supplymeans between the equilibrium voltage and the special charging voltage,and a charge time predicting means for estimating a time required tofully charge the secondary battery basing on the detected electriccurrent, wherein the charge control device controls charge of asecondary battery by first to sixth steps: the first step of applyingthe special charging voltage to the secondary battery set in thecharging equipment for a predetermined time; the second step ofswitching charging voltage applied to the secondary battery from thespecial charging voltage to the equilibrium voltage; the third step ofdetecting electric current flowing through the secondary battery by thecurrent detection means while applying charging the equilibrium voltageto the secondary battery for a short time; the fourth step of predictinga time required to fully charge the secondary battery by the charge timepredicting means basing on the detected electric current; the fifth stepof switching charging voltage applied to the secondary battery from theequilibrium voltage to the special charging voltage; and the sixth stepof halting charge of the secondary battery after the lapse of the timerequired to fully charge the secondary.
 27. A charging equipment for asecondary battery according to claim 26, further comprising: ashort-circuit means for short-circuiting the secondary battery betweenits terminals after applying the special charging voltage for thepredetermined time and before switching charging voltage to theequilibrium voltage.
 28. A charging equipment for a secondary batteryaccording to claim 26 or 27, further comprising: an informational meansfor giving information of the time required to fully charge thesecondary battery, the charging rate of the secondary battery, a chargedcondition of the secondary battery for deciding whether charge of thesecondary battery is finished or not.
 29. A charging equipment for asecondary battery according to claim 26, further comprising: a coolingmeans for cooling an exothermic section in the charging equipment.
 30. Acharging equipment for a secondary battery, comprising: a voltage supplymeans for applying voltage to the secondary battery; a current detectionmeans for detecting electric current flowing through the secondarybattery; and a charge control device for controlling charge of thesecondary battery, the charge control device including a storage meansstoring equilibrium voltage and special charging voltage correspondingto the secondary battery to be charged, the equilibrium voltage forestablishing equilibrium cell potential of the secondary battery in afully charged condition, and the special charging voltage for supplyingthe secondary battery with charging electric current of peak or almostpeak value, wherein the special charging voltage is larger than theequilibrium voltage and does not reach a region of voltage causingirreversible chemical reaction in the secondary battery, a switchingmeans for switching charging voltage supplied by the voltage supplymeans between the equilibrium voltage and the special charging voltage,a charging rate computing means for computing a charging rate of thesecondary battery at the moment when the current detection means detectsthe electric current, and a judging means for judging whether thecharging rate computed by the charging rate computing means is largerthan a preset standard value or not, wherein the charge control devicecontrols charge of a secondary battery by first to fifth steps: thefirst step of applying the special charging voltage to the secondarybattery set in the charging equipment for a predetermined time; thesecond step of switching charging voltage applied to the secondarybattery from the special charging voltage to the equilibrium voltage;the third step of detecting electric current flowing through thesecondary battery by the current detection means while applying theequilibrium voltage to the secondary battery for a short time; thefourth step of computing the charging rate of the secondary battery bythe charging rate computing means at the moment when the electriccurrent is detected; and the fifth step of returning to the first stepand repeating the above steps if the judging means judges that thecomputed value of charging rate is not larger than the standard value;otherwise, halting charge of the secondary battery.
 31. A chargingequipment for a secondary battery according to claim 30, furthercomprising: a short-circuit means for short-circuiting the secondarybattery between its terminals after applying the special chargingvoltage for the predetermined time and before switching charging voltageto the equilibrium voltage.
 32. A charging equipment for a secondarybattery according to claim 30 or 31, further comprising: aninformational means for giving information of the time required to fullycharge the secondary battery, the charging rate of the secondarybattery, or a charged condition of the secondary battery for decidingwhether charge of the secondary battery is finished or not.
 33. Acharging equipment for a secondary battery according to claim 30,further comprising: a cooling means for cooling an exothermic section inthe charging equipment.
 34. A charging equipment for a secondary batterycomprising: a circuit connecting a secondary battery and a capacitor toa power source in parallel, a switching means for making/breaking aclosed loop circuit connecting the secondary battery to the capacitor, achecking power source for which applying special charging voltage to thesecondary battery; a current detection means for detecting electriccurrent flowing to the secondary battery; and a current judging meansfor judging whether electric current detected by the current detectionmeans during application of the special charging voltage is larger thanpreset standard electric current for finishing charging, wherein, whilethe closed loop circuit is broken, the power source applies voltage tothe capacitor for a determined time so as to store electricity in thecapacitor, and then the closed loop circuit is made so as to transmitthe electricity stored in the capacitor to the secondary battery,thereby charging the secondary battery, wherein, while the closed loopcircuit is broken, the checking power source applies the secondarybattery with the special charging voltage, and electric current flowingto the secondary battery from the checking power source is detected andcompared with the standard electric current for finishing charging, andwherein, if the detected electric current is larger than the standardelectric current for finishing charging, said storage of electricity inthe capacitor and transmission of electricity to the secondary batteryare repeated; otherwise, charge of the secondary battery is halted. 35.A charging equipment for a secondary battery according to claim 34,wherein the special charging voltage is equilibrium voltage equalingelectromotive force of the secondary battery in a fully chargedcondition.
 36. A charging equipment for a secondary battery accordingclaim 34 or 35, further comprising: a cooling means for cooling anexothermic section in the charging equipment.
 37. A charging equipmentfor a plurality of secondary batteries comprising: a charging voltagecontrol means for applying charging voltage to a secondary battery; acontrol means for monitoring a charged condition of the secondarybattery; a battery switching means for switching a secondary batteryselected among the plurality of secondary batteries to be charged basingon a signal for finishing charging issued from the control means; achecking voltage control means for applying equilibrium voltage to asecondary battery while monitoring a charged condition of the secondarybattery, the equilibrium voltage for establishing equilibrium cellpotential of the secondary battery in a fully charged condition; avoltage switching means for switching voltage between the chargingvoltage and the equilibrium voltage, that is, checking voltage; and acurrent detection means for detecting electric current flowing throughthe secondary battery to which the check voltage is applied, wherein thecontrol means monitors a charged condition of the secondary batterybasing on the signal from the current detection means.
 38. A chargingequipment for a plurality of secondary batteries according to claim 37,wherein the charging voltage is a special charging voltage for supplyingthe secondary battery with charging electric current of peak or almostpeak value, and wherein the special charging voltage is larger thanequilibrium voltage for establishing equilibrium cell potential of thesecondary battery in a fully charged condition and does not reach aregion of voltage causing irreversible chemical reaction in thesecondary battery.
 39. A charging equipment for a secondary batteryaccording to claim 37, further comprising: an informational means forgiving information of a time required to charge each secondary battery,a charging rate of each secondary battery, a charged condition of eachsecondary battery whether charge of the secondary battery is finished ornot.
 40. A charging equipment for a secondary battery claim 37, furthercomprising: a cooling means for cooling an exothermic section in thecharging equipment.
 41. A charging equipment for a secondary battery,comprising: a voltage supply means for applying voltage to the secondarybattery; a voltage detection means for detecting voltage of thesecondary battery; and a judging means for judging whether voltage ofthe charged secondary battery detected by the voltage detection means islarger than recharging voltage, which is smaller than equilibriumvoltage for establishing equilibrium cell potential of the secondarybattery in a fully charged condition, or not, wherein, if the judgingmeans judges that the detected voltage of the charged secondary batteryis not larger than the recharging voltage, the secondary battery isrecharged by supplying charging voltage from the voltage supply means.42. A charging method for a secondary battery, comprising the steps of:(1) previously storing equilibrium voltage and special charging voltagecorresponding to the secondary battery to be charged, the equilibriumvoltage for establishing equilibrium cell potential of the secondarybattery in a fully charged condition, and the special charging voltagefor supplying the secondary battery with charging electric current ofpeak or almost peak value, wherein the special charging voltage islarger than the equilibrium voltage and does not reach a region ofvoltage causing irreversible chemical reaction in the secondary battery;(2) applying the special charging voltage to the secondary battery for adetermined time; (3) switching charging voltage applied to the secondarybattery from the special charging voltage to the equilibrium voltage;(4) detecting electric current flowing through the secondary batterywhile applying the equilibrium voltage to the secondary battery for ashort time; (5) comparing the detected electric current with standardelectric current for finishing charging; and (6) returning to the step(2) and iterating the above steps when the detected electric current islarger than standard electric current; otherwise halting charge of thesecondary battery.
 43. A charging method for a secondary battery,comprising: previously storing n (n is a natural number more than 1)equilibrium voltages and n special charging voltages for charging ndifferent kinds of secondary batteries, each of the equilibrium voltagesfor establishing equilibrium cell potential of the secondary battery ina fully charged condition, and each of the special charging voltages forsupplying the secondary battery with charging electric current of peakor almost peak value, wherein each of the special charging voltages islarger than the corresponding equilibrium voltage and does not reach aregion of voltage causing irreversible chemical reaction in thecorresponding secondary battery; and charging a secondary battery byfirst to eighth steps, the first step of initializing a counter variablek (k=1,2, . . . , n) to 1; the second step of applying the kth smallestspecial charging voltage of then special charging voltages to thesecondary battery for a predetermined time; the third step of jumping tothe sixth step if k is equal to n; the fourth step of detecting voltageapplied to the secondary battery while applying the kth smallest specialcharging voltage to the secondary battery for the predetermined time;the fifth step of incrementing the rank of k by 1 and returning to thesecond step if the detected voltage is larger than the kth smallestspecial charging voltage; otherwise passing to the sixth step; the sixthstep of switching charging voltage applied to the secondary battery fromthe kth smallest special charging voltage to the kth smallestequilibrium voltage of the n equilibrium voltages; and the seventh stepof detecting electric current flowing through the secondary batterywhile applying the kth smallest equilibrium voltage to the secondarybattery for a short time; and the eighth step of returning to the secondstep and iterating the above steps if the detected electric current islarger than standard electric current for finishing charging; otherwise,halting charge of the secondary battery.
 44. A charging method for asecondary battery, comprising: previously storing n (n is a naturalnumber more than 1) equilibrium voltages and n special charging voltagesfor charging n different kinds of secondary batteries, each of theequilibrium voltages for establishing equilibrium cell potential of thesecondary battery in a fully charged condition, and each of the specialcharging voltages for supplying the secondary battery with chargingelectric current of peak or almost peak value, wherein each of thespecial charging voltages is larger than the corresponding equilibriumvoltage and does not reach a region of voltage causing irreversiblechemical reaction in the corresponding secondary battery; and charging asecondary battery by first to eighth steps, the first step ofinitializing a counter variable k (k=1,2, . . . , n) to 1; the secondstep of applying the kth smallest special charging voltage of thenspecial charging voltages to the secondary battery for a predeterminedtime; the third step of jumping to the sixth step if k is equal to n;the fourth step of detecting voltage applied to the secondary batterywhile applying the kth smallest special charging voltage to thesecondary battery for the predetermined time; the fifth step of passingto the sixth step if the voltage detection is the first time or avoltage difference between present and past voltages detected duringapplication of the kth smallest special charging voltage is within apreset range; otherwise, incrementing the rank of k by 1 and returningto the second step; the sixth step of switching charging voltage appliedto the secondary battery from the kth smallest special charging voltageto the kth smallest equilibrium voltage of the n equilibrium voltages;and the seventh step of detecting electric current flowing through thesecondary battery while applying charging voltage of the kth smallestequilibrium voltage to the secondary battery for a short time; and theeighth step of returning to the second step and iterating the abovesteps if the detected electric current is larger than standard electriccurrent for finishing charging; otherwise, halting charge of thesecondary battery.